### Installation

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Install the Scopus API library using Composer.

```APIDOC
## Installation

### Description
Install the Scopus API library using Composer.

### Command
```bash
composer require hbll-collection-development/scopus-api
```
```

--------------------------------

### Install Scopus API Client

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Install the Scopus API client using Composer. This command fetches and installs the necessary package for your project.

```bash
composer require hbll-collection-development/scopus-api
```

--------------------------------

### start($start)

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/affiliation-retrieval.md

Sets the starting position for paginated results.

```APIDOC
## start($start)

### Description

Set the starting position for pagination.

### Parameters

- **$start** (int) - Required - Zero-indexed start position.

### Returns

`$this` for method chaining.
```

--------------------------------

### Set Pagination Start Position

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/affiliation-search.md

Use the `start` method to define the starting position for paginating results. This is a zero-indexed position.

```php
public function start(int $start): self
```

--------------------------------

### startref($startref)

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/abstract-retrieval.md

Sets the starting position for reference retrieval in the abstract data.

```APIDOC
## Method `startref($startref)`

### Description
Set the starting position for reference retrieval.

### Parameters
#### Path Parameters
- **$startref** (int) - Required - Starting index for references

### Returns
`$this` for method chaining
```

--------------------------------

### Execute Search and Get Citations Overview

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/citations-overview.md

Executes the retrieval request to get citation overview data. The response format can be JSON or XML. This method is used after setting necessary parameters like scopus_id, count, and start.

```php
public function search(): string
```

```php
$citationsOverview = new \Scopus\CitationsOverview('your-api-key');
$results = $citationsOverview
    ->scopus_id('85028623301')
    ->count(10)
    ->start(0)
    ->search();

$data = json_decode($results, true);
foreach ($data['abstracts-retrieval-response']['citation-overview'] as $citation) {
    echo $citation['dc:title'] . "\n";
}
```

--------------------------------

### Method Documentation Details

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Detailed documentation is provided for each method, including signatures, parameters, return types, errors, and examples.

```APIDOC
## Method Documentation

Each method in the Scopus API is documented with:

- **Full Signature**: Includes parameter types.
- **Parameter Table**: Details name, type, required status, default value, and description for each parameter.
- **Return Type**: Specifies the return type and its meaning.
- **Throws/Error Conditions**: Lists potential exceptions and their triggers.
- **Usage Example**: Demonstrates how to use the method.
- **Method Chaining**: Support for chaining methods is indicated where applicable.
```

--------------------------------

### Set Pagination Start

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-search.md

Specify the zero-indexed starting position for paginating results. This method supports chaining.

```php
$authorSearch->start(50);
```

--------------------------------

### Basic Usage

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Example of how to search for affiliations and parse the results.

```APIDOC
## Basic Usage

### Description
Example of how to search for affiliations and parse the results.

### Code Example
```php
require_once 'vendor/autoload.php';

// Search for affiliations
$affiliationSearch = new \Scopus\AffiliationSearch('your-api-key');
$results = $affiliationSearch
    ->query('AFFIL(MIT)')
    ->count(25)
    ->search();

// Parse results
$data = json_decode($results, true);
echo $data['search-results']['opensearch:totalResults'];
```
```

--------------------------------

### Install Scopus API PHP SDK via Composer

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

Use Composer to install the Scopus API PHP SDK. Add this to your project's dependencies.

```json
"require": {
    "hbll-collection-development/scopus-api": "^1.0"
}
```

--------------------------------

### Method Chaining Example

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-base.md

Demonstrates fluid API patterns by chaining multiple method calls. All methods return `$this` to enable this.

```php
$results = $search
    ->query('TITLE(Machine Learning)')
    ->count(10)
    ->start(0)
    ->sort('+citedby-count')
    ->httpAccept('application/json')
    ->search();
```

--------------------------------

### Set Reference Retrieval Start Position

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-base.md

Specify the starting index for retrieving reference lists. This is useful when dealing with large sets of references.

```php
public function startref(int $startref): self
```

--------------------------------

### Set Starting Position for Pagination

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-search.md

Determine the starting point for paginating search results. This parameter uses zero-based indexing.

```php
$scopusSearch->start(50);
```

--------------------------------

### Abstract Retrieval JSON Response Example

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

An example of the JSON response structure for an abstract retrieval request.

```json
{
  "abstracts-retrieval-response": {
    "coredata": {
      "prism:url": "https://api.elsevier.com/content/abstract/scopus_id/85028623301",
      "dc:identifier": "SCOPUS_ID:85028623301",
      "link": [
        {
          "@href": "https://api.elsevier.com/content/abstract/scopus_id/85028623301",
          "@rel": "self",
          "@_fa": "true"
        }
      ]
    }
  }
}
```

--------------------------------

### Date Format Examples

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/types.md

Illustrates the supported date formats for filtering, including specific dates, years, and date ranges.

```text
YYYY-MM-DD                  # Specific date
YYYY                        # Specific year
[YYYY-MM-DD TO YYYY-MM-DD]  # Date range
```

--------------------------------

### Retrieve Abstract by Specific Scopus ID Example

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

A concrete example of initializing AbstractRetrieval with a specific Scopus ID '85028623301' to retrieve its abstract.

```php
$abstractRetrieval = new \Scopus\AbstractRetrieval('85028623301', 'scopusId', 'API-KEY');
```

--------------------------------

### Scopus Search JSON Response Example

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

An example of the JSON response structure returned by a Scopus search query.

```json
{
  "search-results": {
    "opensearch:totalResults": "432",
    "opensearch:startIndex": "0",
    "opensearch:itemsPerPage": "1",
    "opensearch:Query": {
      "@role": "request",
      "@searchTerms": "TITLE(Tragedy of the Commons)",
      "@startPage": "0"
    },
    "link": [
      {
        "@_fa": "true",
        "@ref": "self",
        "@href": "https://api.elsevier.com/content/search/scopus?start=0&count=1&query=TITLE%28Tragedy+of+the+Commons%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      },
      {
        "@_fa": "true",
        "@ref": "first",
        "@href": "https://api.elsevier.com/content/search/scopus?start=0&count=1&query=TITLE%28Tragedy+of+the+Commons%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      },
      {
        "@_fa": "true",
        "@ref": "next",
        "@href": "https://api.elsevier.com/content/search/scopus?start=1&count=1&query=TITLE%28Tragedy+of+the+Commons%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      },
      {
        "@_fa": "true",
        "@ref": "last",
        "@href": "https://api.elsevier.com/content/search/scopus?start=431&count=1&query=TITLE%28Tragedy+of+the+Commons%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      }
    ],
    "entry": [
      {
        "@_fa": "true",
        "link": [
          {
            "@_fa": "true",
            "@ref": "self",
            "@href": "https://api.elsevier.com/content/abstract/scopus_id/85028623301"
          },
          {
            "@_fa": "true",
            "@ref": "author-affiliation",
            "@href": "https://api.elsevier.com/content/abstract/scopus_id/85028623301?field=author,affiliation"
          },
          {
            "@_fa": "true",
            "@ref": "scopus",
            "@href": "https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85028623301&origin=inward"
          },
          {
            "@_fa": "true",
            "@ref": "scopus-citedby",
            "@href": "https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85028623301&origin=inward"
          }
        ],
        "prism:url": "https://api.elsevier.com/content/abstract/scopus_id/85028623301",
        "dc:identifier": "SCOPUS_ID:85028623301",
        "eid": "2-s2.0-85028623301",
        "dc:title": "An allometric tragedy of the commons: Response to the article “Evaluation of models capacity to predict size spectra parameters in ecosystems under stress”",
        "dc:creator": "Mulder C.",
        "prism:publicationName": "Ecological Indicators",
        "prism:issn": "1470160X",
        "prism:volume": "84",
        "prism:pageRange": "161-164",
        "prism:coverDate": "2018-01-01",
        "prism:coverDisplayDate": "January 2018",
        "prism:doi": "10.1016/j.ecolind.2017.08.042",
        "pii": "S1470160X17305320",
        "citedby-count": "0",
        "affiliation": [
          {
            "@_fa": "true",
            "affilname": "National Institute of Public Health and the Environment",
            "affiliation-city": "Bilthoven",
            "affiliation-country": "Netherlands"
          }
        ],
        "prism:aggregationType": "Journal",
        "subtype": "le",
        "subtypeDescription": "Letter",
        "source-id": "20292"
      }
    ]
  }
}
```

--------------------------------

### Set Start Position

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/serial-title.md

Sets the starting position for paginated results. This is a zero-indexed value.

```APIDOC
## start($start)

### Description

Set the starting position for pagination.

### Method

```php
public function start(int $start): self
```

### Parameters

#### Path Parameters

- **$start** (int) - Required - Zero-indexed start position

### Returns

`$this` for method chaining
```

--------------------------------

### Configuring Scopus Search via Method Chaining

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Illustrates the fluent API pattern for configuring a Scopus search query, including query parameters, count, start, sort order, and view/field options.

```php
$results = (new \Scopus\ScopusSearch('your-api-key'))
    ->query('TITLE(Machine Learning)')
    ->count(25)
    ->start(0)
    ->sort('+citedby-count')
    ->httpAccept('application/json')
    ->view('STANDARD')
    ->field('all')
    ->search();
```

--------------------------------

### Example: Search for Serial Title Metadata

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/serial-title.md

Demonstrates how to instantiate the SerialTitle class, set an ISSN, specify fields to retrieve, execute a search, and parse the JSON response to access the serial title.

```php
$serialTitle = new \Scopus\SerialTitle('your-api-key');
$results = $serialTitle
    ->issn('1470-160X')
    ->field('all')
    ->search();

$data = json_decode($results, true);
echo $data['serial-metadata-response']['entry'][0]['dc:title'];
```

--------------------------------

### Execute Search and Get Results

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-search.md

Executes the configured search request. The response format (JSON or XML) depends on the httpAccept setting. Throws a RequestException on HTTP failure.

```php
public function search(): string
```

```php
$results = $authorSearch->search();
$data = json_decode($results, true);
echo $data['search-results']['opensearch:totalResults'];
```

--------------------------------

### Parser API

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Documentation for the Parser class, covering key normalization, extension examples, and recursive parsing behavior.

```APIDOC
## Parser API Reference

### Description
Reference for the Parser class, documenting key normalization, providing extension examples, and explaining its recursive parsing behavior.

### Functionality
- Key normalization.
- Recursive parsing.

### Examples
- Extension examples for the parser.
```

--------------------------------

### Nested JSON Normalization Example

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/parser.md

Illustrates the recursive key normalization applied to nested JSON structures, including attributes and namespaced keys.

```json
// Original Scopus JSON
{
  "search-results": {
    "opensearch:totalResults": "432",
    "link": [
      {
        "@_fa": "true",
        "@ref": "self",
        "@href": "https://api.elsevier.com/..."
      }
    ]
  }
}

// After parsing and normalization:
[
  "search_results" => [
    "opensearch_totalResults" => "432",
    "link" => [
      [
        "fa" => "true",
        "ref" => "self",
        "href" => "https://api.elsevier.com/..."
      ]
    ]
  ]
]
```

--------------------------------

### Citations Overview

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Get an overview of citations for abstracts.

```APIDOC
## GET https://api.elsevier.com/content/abstract/citations

### Description
Get citations overview.

### Method
GET

### Endpoint
https://api.elsevier.com/content/abstract/citations
```

--------------------------------

### CitationsOverview

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Get citing articles overview using the CitationsOverview API client.

```APIDOC
## CitationsOverview

### Description
Get citing articles overview.

### Method
GET

### Endpoint
/v2/citation-overview

### Parameters
#### Query Parameters
- **eid** (string) - Required - The EID (Electronic Identifier) of the document.

### Request Example
```json
{
  "eid": "2-s2.0-12345678901"
}
```

### Response
#### Success Response (200)
- **citing_articles_count** (string) - The number of articles that cite this document.

#### Response Example
```json
{
  "citing_articles_count": "100"
}
```
```

--------------------------------

### Author Search API

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Documentation for the AuthorSearch class, including co_author() method and method chaining examples.

```APIDOC
## Author Search API Reference

### Description
Full reference for the AuthorSearch class, including documentation for the `co_author()` method and examples of method chaining.

### Methods
- `co_author()`
- Method chaining examples.

### Parameters
- Documented within the respective method details.

### Return Types
- Documented within the respective method details.

### Examples
- Method chaining examples provided.
```

--------------------------------

### Basic Affiliation Search

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Perform a basic search for affiliations using the Scopus API. This example demonstrates initializing the search, setting a query, specifying the count, and executing the search.

```php
require_once 'vendor/autoload.php';

// Search for affiliations
$affiliationSearch = new \Scopus\AffiliationSearch('your-api-key');
$results = $affiliationSearch
    ->query('AFFIL(MIT)')
    ->count(25)
    ->search();

// Parse results
$data = json_decode($results, true);
echo $data['search-results']['opensearch:totalResults'];
```

--------------------------------

### Example JSON Response for Author Search

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

This is a sample JSON response structure for an author search query. It includes details about the search results, query parameters, and individual author entries.

```json
{
  "search-results": {
    "opensearch:totalResults": "1",
    "opensearch:startIndex": "0",
    "opensearch:itemsPerPage": "1",
    "opensearch:Query": {
      "@role": "request",
      "@searchTerms": "AUTHLASTNAME(Howland) AND AUTHFIRST(J) AND AF-ID(60006832)",
      "@startPage": "0"
    },
    "link": [
      {
        "@_fa": "true",
        "@ref": "self",
        "@href": "https://api.elsevier.com/content/search/author?start=0&count=25&query=AUTHLASTNAME%28Howland%29+AND+AUTHFIRST%28J%29+AND+AF-ID%2860006832%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      },
      {
        "@_fa": "true",
        "@ref": "first",
        "@href": "https://api.elsevier.com/content/search/author?start=0&count=25&query=AUTHLASTNAME%28Howland%29+AND+AUTHFIRST%28J%29+AND+AF-ID%2860006832%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      }
    ],
    "entry": [
      {
        "@_fa": "true",
        "link": [
          {
            "@_fa": "true",
            "@ref": "self",
            "@href": "https://api.elsevier.com/content/author/author_id/14071559700"
          },
          {
            "@_fa": "true",
            "@ref": "search",
            "@href": "https://api.elsevier.com/content/search/author?query=au-id%2814071559700%29"
          },
          {
            "@_fa": "true",
            "@ref": "scopus-citedby",
            "@href": "https://www.scopus.com/author/citedby.uri?partnerID=HzOxMe3b&citedAuthorId=14071559700&origin=inward"
          },
          {
            "@_fa": "true",
            "@ref": "scopus-author",
            "@href": "https://www.scopus.com/authid/detail.uri?partnerID=HzOxMe3b&authorId=14071559700&origin=inward"
          }
        ],
        "prism:url": "https://api.elsevier.com/content/author/author_id/14071559700",
        "dc:identifier": "AUTHOR_ID:14071559700",
        "eid": "9-s2.0-14071559700",
        "preferred-name": {
          "surname": "Howland",
          "given-name": "Jared L.",
          "initials": "J.L."
        },
        "name-variant": [
          {
            "@_fa": "true",
            "surname": "Howland",
            "given-name": "Jared",
            "initials": "J."
          }
        ],
        "document-count": "4",
        "subject-area": [
          {
            "@abbrev": "SOCI",
            "@frequency": "4",
            "$": "Social Sciences (all)"
          },
          {
            "@abbrev": "COMP",
            "@frequency": "1",
            "$": "Computer Science (all)"
          }
        ],
        "affiliation-current": {
          "affiliation-url": "https://api.elsevier.com/content/affiliation/affiliation_id/60006832",
          "affiliation-id": "60006832",
          "affiliation-name": "Brigham Young University",
          "affiliation-city": "Provo",
          "affiliation-country": "United States"
        }
      }
    ]
  }
}
```

--------------------------------

### Execute Search and Get Results

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-search.md

Executes the search request and returns the results as a JSON or XML string. This method is crucial for retrieving search data.

```php
public function search(): string
```

```php
$results = $scopusSearch->search();
$data = json_decode($results, true);
echo $data['search-results']['opensearch:totalResults'];
foreach ($data['search-results']['entry'] as $entry) {
    echo $entry['dc:title'] . "\n";
}
```

--------------------------------

### Execute Search and Get Results

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/serial-title.md

Executes the retrieval request based on the configured parameters and returns the response as a JSON or XML string. Ensure that the HTTP accept header is correctly set prior to calling this method. This method can throw a GuzzleHttp\Exception\RequestException if the HTTP request fails.

```php
public function search(): string
```

--------------------------------

### Configuration Reference

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Documentation for constructor parameters, query parameter methods, validation rules, and HTTP client configuration.

```APIDOC
## Configuration Reference

### Description
Documents constructor parameters, all 40+ query parameter methods, parameter validation rules, and HTTP client configuration.

### Parameters
- Constructor parameters.
- 40+ query parameter methods.
- Parameter validation rules.

### Validation
- ISSN validation details.
- ID type validation.

### Configuration
- HTTP client configuration.
- Environment variable guidance.

### Examples
- Parameter validation examples.
```

--------------------------------

### Instantiate SubjectClassifications

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/subject-classifications.md

Initialize the SubjectClassifications client for either 'scopus' or 'scidir' systems. Ensure your API key is provided.

```php
require_once 'vendor/autoload.php';

$subjectClassifications = new 
Scopus\SubjectClassifications('scopus', 'your-api-key');
$results = $subjectClassifications
    ->code('1402')
    ->search();
```

--------------------------------

### Instantiate CitationsOverview

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/citations-overview.md

Initialize the CitationsOverview class with your Scopus API key and an optional timeout. The API key is required for authentication.

```php
require_once 'vendor/autoload.php';

$citationsOverview = new 
	Scopus\CitationsOverview('your-api-key');
$results = $citationsOverview
    ->scopus_id('85028623301')
    ->count(25)
    ->search();
```

--------------------------------

### Instantiate Custom Parser

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/parser.md

Demonstrates how to instantiate a custom parser with a JSON response and retrieve normalized data. Requires a custom class extending Parser.

```php
$jsonResponse = '{"search-results": {"opensearch:totalResults": "100"}}';
$parser = new CustomParser($jsonResponse);
$data = $parser->retrieve();
// Result: ["search_results" => ["opensearch_totalResults" => "100"]]
```

--------------------------------

### Constructor

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-search.md

Initializes a new instance of the ScopusSearch class. Requires an API key for authentication and allows setting an optional timeout.

```APIDOC
## Constructor

Initializes a new instance of the ScopusSearch class.

### Parameters

- **$apiKey** (string) - Required - Scopus API key for authentication
- **$timeout** (float) - Optional - HTTP request timeout in seconds (default: 30.0)

### Returns

`ScopusSearch` instance

### Throws

`Exception` if apiKey is empty or not provided

### Example

```php
require_once 'vendor/autoload.php';

$scopusSearch = new \Scopus\ScopusSearch('your-api-key');
$results = $scopusSearch
    ->query('TITLE(Artificial Intelligence)')
    ->count(25)
    ->search();
```
```

--------------------------------

### Configuration Documentation Details

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Guidance on configuring the Scopus API client, including authentication, timeouts, and parameter handling.

```APIDOC
## Configuration Documentation

Configuration options include:

- **Constructor Parameters**: Settings available during client initialization.
- **Query Parameter Methods**: Over 40 methods for configuring query parameters.
- **Parameter Validation Rules**: Rules governing parameter values.
- **HTTP Client Configuration**: Settings for the underlying HTTP client.
- **Timeout Configuration**: Setting request timeouts.
- **Authentication Options**: Details on authentication methods.
- **Response Format Configuration**: Options for response formats.
- **Method Chaining Pattern**: Explanation of the method chaining approach.
```

--------------------------------

### Instantiate AuthorSearch

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-search.md

Initialize the AuthorSearch client with your Scopus API key. The timeout parameter is optional.

```php
require_once 'vendor/autoload.php';

$authorSearch = new \Scopus\AuthorSearch('your-api-key');
$results = $authorSearch
    ->query('AUTHLASTNAME(Smith) AND AUTHFIRST(John)')
    ->count(10)
    ->search();
```

--------------------------------

### Abstract Retrieval Initialization Options

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

Demonstrates alternative ways to initialize the AbstractRetrieval client using different identifier types like EID, DOI, PII, PubMed ID, or PUI.

```php
$abstractRetrieval = new \Scopus\AbstractRetrieval('EID', 'eid', 'API-KEY');
```

```php
$abstractRetrieval = new \Scopus\AbstractRetrieval('DOI', 'doi', 'API-KEY');
```

```php
$abstractRetrieval = new \Scopus\AbstractRetrieval('PII', 'pii', 'API-KEY');
```

```php
$abstractRetrieval = new \Scopus\AbstractRetrieval('PUBMED-ID', 'pubmedId', 'API-KEY');
```

```php
$abstractRetrieval = new \Scopus\AbstractRetrieval('PUI', 'pui', 'API-KEY');
```

--------------------------------

### Citations Count

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Get the citation count for abstracts.

```APIDOC
## GET https://api.elsevier.com/content/abstract/citation-count

### Description
Get citation count.

### Method
GET

### Endpoint
https://api.elsevier.com/content/abstract/citation-count
```

--------------------------------

### Constructor

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/subject-classifications.md

Initializes the SubjectClassifications client. You can specify the classification system ('scidir' or 'scopus'), your API key, and an optional timeout.

```APIDOC
## Constructor

```php
new \Scopus\SubjectClassifications($searchType, $apiKey = null, $timeout = null)
```

### Parameters

#### Path Parameters
- **$searchType** (string) - Required - Classification system: `scidir` or `scopus`
- **$apiKey** (string) - Required - Scopus API key for authentication
- **$timeout** (float) - Optional - HTTP request timeout in seconds (default: 30.0)

### Throws

- `Exception` if $apiKey is empty
- `Exception` if $searchType is not `scidir` or `scopus`

### Example

```php
require_once 'vendor/autoload.php';

$subjectClassifications = new \Scopus\SubjectClassifications('scopus', 'your-api-key');
$results = $subjectClassifications
    ->code('1402')
    ->search();
```
```

--------------------------------

### Method Chaining

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Demonstrates the fluent API pattern using method chaining for constructing search queries.

```APIDOC
## Method Chaining

### Description
All query parameter methods return `$this`, enabling fluent API patterns for constructing search queries.

### Code Example
```php
$results = (new \Scopus\ScopusSearch('api-key'))
    ->query('TITLE(Machine Learning)')
    ->count(50)
    ->start(0)
    ->sort('+citedby-count')
    ->httpAccept('application/json')
    ->search();
```
```

--------------------------------

### CitationsCount

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/README.md

Get citation counts for documents using the CitationsCount API client.

```APIDOC
## CitationsCount

### Description
Get citation counts for documents.

### Method
GET

### Endpoint
/v2/citation-count

### Parameters
#### Query Parameters
- **eid** (string) - Required - The EID (Electronic Identifier) of the document.

### Request Example
```json
{
  "eid": "2-s2.0-12345678901"
}
```

### Response
#### Success Response (200)
- **citation_count** (string) - The total citation count for the document.

#### Response Example
```json
{
  "citation_count": "50"
}
```
```

--------------------------------

### Constructor

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/serial-title.md

Initializes a new instance of the SerialTitle class. Requires an API key for authentication and optionally accepts a timeout value.

```APIDOC
## Constructor

```php
new \Scopus\SerialTitle($apiKey = null, $timeout = null)
```

### Parameters

#### Path Parameters

- **$apiKey** (string) - Required - Scopus API key for authentication
- **$timeout** (float) - Optional - HTTP request timeout in seconds (default: 30.0)

### Returns

`SerialTitle` instance

### Throws

`Exception` if apiKey is empty or not provided

### Example

```php
require_once 'vendor/autoload.php';

$serialTitle = new \Scopus\SerialTitle('your-api-key');
$results = $serialTitle
    ->issn('1234-5678')
    ->search();
```
```

--------------------------------

### Validators API

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Documentation for the Validator abstract base class, including IssnValidator and IsbnValidator with usage examples.

```APIDOC
## Validators API Reference

### Description
Reference for the Validator abstract base class, detailing the IssnValidator (with full algorithm) and IsbnValidator (ISBN-10 and ISBN-13), including usage examples.

### Classes
- `Validator` (abstract base class)
- `IssnValidator`
- `IsbnValidator`

### Functionality
- ISSN validation algorithm.
- ISBN-10 and ISBN-13 validation.

### Examples
- Usage examples for ISSN and ISBN validation.
```

--------------------------------

### Handle API Key from Environment Variable

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Implement logic to retrieve the API key from environment variables and throw an exception if it's not set. This is useful for application-level configuration.

```php
$apiKey = getenv('SCOPUS_API_KEY');
if (!$apiKey) {
    throw new Exception('SCOPUS_API_KEY environment variable not set');
}

$search = new \Scopus\AffiliationSearch($apiKey);
```

--------------------------------

### Instantiate AuthorRetrieval Class

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-retrieval.md

Initialize the AuthorRetrieval class with your Scopus API key and an optional timeout. Ensure the API key is provided for authentication.

```php
require_once 'vendor/autoload.php';

$authorRetrieval = new 
Scopus\AuthorRetrieval('your-api-key');
$results = $authorRetrieval
    ->author_id('14071559700')
    ->search();
```

--------------------------------

### Instantiate ScopusSearch

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-search.md

Create a new instance of the ScopusSearch class. Requires your Scopus API key for authentication. Optionally, you can set an HTTP request timeout.

```php
require_once 'vendor/autoload.php';

$scopusSearch = new \Scopus\ScopusSearch('your-api-key');
$results = $scopusSearch
    ->query('TITLE(Artificial Intelligence)')
    ->count(25)
    ->search();
```

--------------------------------

### Affiliation Search API

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/MANIFEST.md

Documentation for the AffiliationSearch class, including 11 public methods, parameters, return types, and examples.

```APIDOC
## Affiliation Search API Reference

### Description
Full reference for the AffiliationSearch class, detailing its public methods, parameters, return types, and usage examples.

### Methods
- 11 public methods documented.

### Parameters
- Documented within the respective method details.

### Return Types
- Documented within the respective method details.

### Examples
- Usage examples provided for methods.
```

--------------------------------

### Perform Author Search

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

Initializes an AuthorSearch client and performs a search query. Ensure you have your API key and the correct query parameters.

```php
$authorSearch = new \Scopus\AuthorSearch('API-KEY');

$results = $authorSearch
         ->query('AUTHLASTNAME(Howland) AND AUTHFIRST(J) AND AF-ID(60006832)')
         ->search();
```

--------------------------------

### Sort Search Results

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/scopus-search.md

Order the search results based on a specified field. For example, sort by citation count in descending order using '+citedby-count'.

```php
$scopusSearch->sort('+citedby-count');
```

--------------------------------

### Set Sort Order

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-search.md

Sort the search results based on a specified field. For example, '+surname' sorts by surname in ascending order. This method supports chaining.

```php
$authorSearch->sort('+affiliation_city');
```

--------------------------------

### Instantiate SerialTitle with API Key

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/serial-title.md

Initialize the SerialTitle client with your Scopus API key. The timeout parameter can be adjusted for HTTP requests. An exception is thrown if the API key is missing.

```php
require_once 'vendor/autoload.php';

$serialTitle = new \Scopus\SerialTitle('your-api-key');
$results = $serialTitle
    ->issn('1234-5678')
    ->search();
```

--------------------------------

### Validator::make()

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/validators.md

Creates a new instance of a validator using the static constructor pattern. This method is intended to be used to get an instance of a concrete validator class.

```APIDOC
## Validator::make()

### Description
Create a new instance of the validator using static constructor pattern.

### Method
`public static function make(): Validator`

### Returns
New instance of the concrete validator class

### Example
```php
$validator = \Scopus\Validators\IssnValidator::make();
$isValid = $validator->validate('1234-5678');
```
```

--------------------------------

### Initialize AffiliationSearch

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/affiliation-search.md

Instantiate the AffiliationSearch class with your Scopus API key. The timeout parameter is optional and defaults to 30 seconds.

```php
require_once 'vendor/autoload.php';

$affiliationSearch = new \Scopus\AffiliationSearch('your-api-key');
$results = $affiliationSearch
    ->query('AFFIL(Brigham Young University)')
    ->count(25)
    ->search();
```

--------------------------------

### Instantiate CitationsCount Class

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/citations-count.md

Initialize the CitationsCount class with your Scopus API key. The timeout can also be optionally set.

```php
require_once 'vendor/autoload.php';

$citationsCount = new \Scopus\CitationsCount('your-api-key');
$results = $citationsCount
    ->scopus_id('85028623301')
    ->search();
```

--------------------------------

### Using Scopus Parser with SDK Responses

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/parser.md

Demonstrates how to manually use the Scopus Parser class with SDK responses. Requires extending the base Parser class for custom logic.

```php
require_once 'vendor/autoload.php';

$search = new \Scopus\AffiliationSearch('api-key');
$jsonResponse = $search->query('AFFIL(MIT)')->search();

// Manual parsing would need custom extension
// The base Parser class provides key normalization
class MyParser extends \Scopus\Parser { }

```

--------------------------------

### CitationsOverview Constructor

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/citations-overview.md

Initializes the CitationsOverview class with an API key and optional timeout. The API key is required for authentication.

```APIDOC
## Constructor

### Description
Initializes a new instance of the CitationsOverview class.

### Parameters
#### Path Parameters
- **$apiKey** (string) - Required - Scopus API key for authentication.
- **$timeout** (float) - Optional - HTTP request timeout in seconds. Defaults to 30.0.

### Returns
`CitationsOverview` instance

### Throws
`Exception` if apiKey is empty or not provided.

### Example
```php
require_once 'vendor/autoload.php';

$citationsOverview = new \Scopus\CitationsOverview('your-api-key');
$results = $citationsOverview
    ->scopus_id('85028623301')
    ->count(25)
    ->search();
```
```

--------------------------------

### Scopus API Client Constructor

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Instantiate Scopus API client classes with an API key and an optional timeout. The API key is mandatory for authentication.

```php
new \Scopus\AffiliationSearch($apiKey = null, $timeout = null)
```

--------------------------------

### Scopus Search

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

Allows users to search for articles within the Scopus database using various query parameters. The API returns a list of search results, including total count, start index, and items per page, along with links to the results and individual entries.

```APIDOC
## Scopus Search API

### Description
This endpoint allows you to search the Scopus database for articles based on specified criteria. It returns a paginated list of results.

### Method
POST (implied by SDK usage, actual HTTP method not specified in source)

### Endpoint
Not explicitly defined, but likely related to `https://api.elsevier.com/content/search/scopus` based on documentation link.

### Parameters
- **API-KEY**: string - Required - Your API key for authentication.
- **Query**: string - Required - The search query string (e.g., 'TITLE(Tragedy of the Commons)').

### Request Example
```php
$scopusSearch = new \Scopus\ScopusSearch('API-KEY');
$results = $scopusSearch->query('TITLE(Tragedy of the Commons)')->search();
```

### Response
#### Success Response (200)
- **search-results**: object - Contains the search results.
  - **opensearch:totalResults**: string - The total number of results found.
  - **opensearch:startIndex**: string - The starting index of the current results page.
  - **opensearch:itemsPerPage**: string - The number of items per page.
  - **opensearch:Query**: object - Details about the executed query.
  - **link**: array - Links for pagination and self-reference.
  - **entry**: array - An array of article entries matching the query.

#### Response Example
```json
{
  "search-results": {
    "opensearch:totalResults": "432",
    "opensearch:startIndex": "0",
    "opensearch:itemsPerPage": "1",
    "opensearch:Query": {
      "@role": "request",
      "@searchTerms": "TITLE(Tragedy of the Commons)",
      "@startPage": "0"
    },
    "link": [
      {
        "@_fa": "true",
        "@ref": "self",
        "@href": "https://api.elsevier.com/content/search/scopus?start=0&count=1&query=TITLE%28Tragedy+of+the+Commons%29&apiKey=c29c9566c80d7b2dba4db28894ac26ce",
        "@type": "application/json"
      }
    ],
    "entry": [
      {
        "@_fa": "true",
        "link": [
          {
            "@_fa": "true",
            "@ref": "self",
            "@href": "https://api.elsevier.com/content/abstract/scopus_id/85028623301"
          }
        ],
        "prism:url": "https://api.elsevier.com/content/abstract/scopus_id/85028623301",
        "dc:identifier": "SCOPUS_ID:85028623301",
        "eid": "2-s2.0-85028623301",
        "dc:title": "An allometric tragedy of the commons: Response to the article \"Evaluation of models capacity to predict size spectra parameters in ecosystems under stress\"",
        "dc:creator": "Mulder C.",
        "prism:publicationName": "Ecological Indicators",
        "prism:issn": "1470160X",
        "prism:volume": "84",
        "prism:pageRange": "161-164",
        "prism:coverDate": "2018-01-01",
        "prism:coverDisplayDate": "January 2018",
        "prism:doi": "10.1016/j.ecolind.2017.08.042",
        "pii": "S1470160X17305320",
        "citedby-count": "0",
        "affiliation": [
          {
            "@_fa": "true",
            "affilname": "National Institute of Public Health and the Environment",
            "affiliation-city": "Bilthoven",
            "affiliation-country": "Netherlands"
          }
        ],
        "prism:aggregationType": "Journal",
        "subtype": "le",
        "subtypeDescription": "Letter",
        "source-id": "20292"
      }
    ]
  }
}
```
```

--------------------------------

### Basic Scopus API Initialization

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Initialize the AffiliationSearch client with your Scopus API key. You can also specify a custom HTTP request timeout in seconds.

```php
require_once 'vendor/autoload.php';

// Using API key
$search = new \Scopus\AffiliationSearch('your-scopus-api-key');
$results = $search->query('AFFIL(MIT)')->search();

// With custom timeout (60 seconds)
$search = new \Scopus\AffiliationSearch('your-scopus-api-key', 60.0);
```

--------------------------------

### Handle Missing API Key Exception

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Catch exceptions thrown when the API key is not provided during client initialization. The exception message indicates the requirement for an API key.

```php
try {
    $search = new \Scopus\AffiliationSearch(null);
} catch (Exception $e) {
    echo $e->getMessage(); // "You must set the API Key before making a call."
}
```

--------------------------------

### Customizing HTTP Client Timeout

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Demonstrates how to set a custom timeout value for the SDK client instance. Use this for time-sensitive operations.

```php
// 60-second timeout
$search = new \Scopus\AffiliationSearch('your-api-key', 60.0);

// 5-second timeout for time-sensitive applications
$search = new \Scopus\AffiliationSearch('your-api-key', 5.0);
```

--------------------------------

### Initialize AbstractRetrieval by Scopus ID

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/abstract-retrieval.md

Instantiate the AbstractRetrieval class with a Scopus ID, specifying the ID type and API key. Ensure the 'vendor/autoload.php' is included for class loading.

```php
require_once 'vendor/autoload.php';

// By Scopus ID
$abstractRetrieval = new \Scopus\AbstractRetrieval('85028623301', 'scopusId', 'your-api-key');
$results = $abstractRetrieval->search();
```

--------------------------------

### insttoken

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/citations-overview.md

Sets an institutional token for authentication. This method is chainable.

```APIDOC
## insttoken($insttoken)

### Description
Sets an institutional token for authentication.

### Method
```php
public function insttoken(string $insttoken): self
```

### Parameters
#### Path Parameters
- **$insttoken** (string) - Yes - Institutional token

### Returns
`$this` for method chaining
```

--------------------------------

### insttoken

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/serial-title.md

Sets an institutional token for authentication. This method is chainable.

```APIDOC
## insttoken($insttoken)

### Description
Sets an institutional token for authentication.

### Method
Set

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```php
$serialTitle->insttoken('your-institutional-token');
```

### Response
#### Success Response
Returns `$this` for method chaining.

#### Response Example
(Method chaining, no direct response body)
```

--------------------------------

### Set HTTP Accept Header

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-retrieval.md

Configure the response format by setting the HTTP Accept header using the httpAccept method. Supported formats include 'application/json' and 'application/xml'.

```php
$authorRetrieval->httpAccept('application/json');
```

--------------------------------

### Catching General Exceptions in PHP

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/errors.md

Demonstrates how to catch generic exceptions thrown by the Scopus SDK. This is useful for general error handling when specific error types are not anticipated.

```php
try {
    $search = new \Scopus\AffiliationSearch(null);
} catch (Exception $e) {
    echo $e->getMessage();
    echo $e->getCode();
}
```

--------------------------------

### Default GuzzleHttp Client Configuration

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/configuration.md

Shows the default configuration used by the SDK's GuzzleHttp Client, including timeout and headers. These can be overridden.

```php
$client = new Client([
    'timeout' => 30.0,  // Overridable via $timeout constructor parameter
    'headers' => [
        'Accept' => 'application/json',  // Overridable via httpAccept()
    ],
]);
```

--------------------------------

### AuthorSearch Constructor

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/author-search.md

Initializes a new instance of the AuthorSearch class. Requires an API key for authentication and allows setting an optional timeout.

```APIDOC
## Constructor

### Description
Initializes a new instance of the AuthorSearch class. Requires an API key for authentication and allows setting an optional timeout.

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Method Signature
`new \Scopus\AuthorSearch($apiKey = null, $timeout = null)`

### Parameters
- **$apiKey** (string) - Required - Scopus API key for authentication
- **$timeout** (float) - Optional - HTTP request timeout in seconds (default: 30.0)

### Returns
`AuthorSearch` instance

### Throws
`Exception` if apiKey is empty or not provided

### Example
```php
require_once 'vendor/autoload.php';

$authorSearch = new \Scopus\AuthorSearch('your-api-key');
$results = $authorSearch
    ->query('AUTHLASTNAME(Smith) AND AUTHFIRST(John)')
    ->count(10)
    ->search();
```
```

--------------------------------

### search()

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/affiliation-search.md

Executes the configured search request and returns the response.

```APIDOC
## search()

### Description
Execute the search request and return the response.

### Method
Not applicable (SDK method)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Returns
JSON or XML string (depending on `httpAccept` setting) containing search results

### Throws
`GuzzleHttp\Exception\RequestException` if the HTTP request fails

### Example
```php
$results = $affiliationSearch->search();
$data = json_decode($results, true);
echo $data['search-results']['opensearch:totalResults'];
```
```

--------------------------------

### Perform Affiliation Search (JSON)

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/README.md

Initialize the AffiliationSearch with your API key and perform a search query. Defaults to JSON response.

```php
$affiliationSearch = new \Scopus\AffiliationSearch('API-KEY');

$results = $affiliationSearch
         ->query('AFFIL(Brigham Young University)')
         ->count(1)
         ->search();
```

--------------------------------

### httpAccept

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/api-reference/citations-overview.md

Sets the response format using the HTTP Accept header.

```APIDOC
## httpAccept

### Description
Sets the desired response format by specifying the MIME type in the HTTP Accept header.

### Method
`httpAccept(string $httpAccept): self`

### Parameters
#### Path Parameters
- **$httpAccept** (string) - Required - MIME type (e.g., `application/json`, `application/xml`).

### Returns
`$this` for method chaining.
```

--------------------------------

### Handling Missing API Key Exception

Source: https://github.com/hbll-collection-development/scopus-api/blob/master/_autodocs/errors.md

Catch a specific exception when the API key is not provided to the constructor. Recovery involves providing a valid Scopus API key.

```php
try {
    $search = new \Scopus\AffiliationSearch(null);
} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
    // Handle missing API key
}
```