### Install PHPOAIPMH with Composer

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Include the PHPOAIPMH library and Guzzle HTTP client in your composer.json file for installation.

```json
{
    "require": {
        "caseyamcl/phpoaipmh": "^3.0",
        "guzzlehttp/guzzle":   "^7.0"
    }
}
```

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

### Run Project Tests

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/CONTRIBUTING.md

Execute the project's test suite using PHPUnit. Ensure you have PHPUnit installed and configured.

```bash
$ phpunit
```

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

### Setup OAI-PMH Endpoint Client

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Demonstrates two ways to set up an OAI-PMH endpoint client: using the quick 'build' method or manually creating a Client and Endpoint instance.

```php
// Quick and easy 'build' method 
$myEndpoint = 	\Phpoaipmh\Endpoint::build('http://some.service.com/oai');

// Or, create your own client instance and pass it to `Endpoint::__construct()` 
$client = new 	\Phpoaipmh\Client('http://some.service.com/oai');
$myEndpoint = new 	\Phpoaipmh\Endpoint($client);
```

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

### Install Guzzle Param Middleware

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Install the emarref/guzzle-param-middleware using Composer. This middleware allows for adding arbitrary query parameters to Guzzle requests.

```bash
$composer require emarref/guzzle-param-middleware
```

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

### Install Guzzle Retry Middleware

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Install the Guzzle-Retry-Middleware using Composer. This library helps automatically handle OAI-PMH endpoint rate limiting rules.

```bash
composer require caseyamcl/guzzle_retry_middleware
```

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

### Get Basic Endpoint Information

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Retrieve the identify information from an OAI-PMH endpoint, which returns a SimpleXMLElement object. Also shows how to list all available metadata formats, returning an iterator of SimpleXMLElement objects.

```php
// Result will be a SimpleXMLElement object
$result = $myEndpoint->identify();
var_dump($result);

// Results will be iterator of SimpleXMLElement objects
$results = $myEndpoint->listMetadataFormats();
foreach($results as $item) {
    var_dump($item);
}
```

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

### Get Total Record Count

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Retrieve the total number of records from an endpoint if available. Returns 'unknown' if the count is not provided.

```php
$iterator = $myEndpoint->listRecords('someMetaDataFormat');
echo "Total count is " . ($iterator->getTotalRecordCount() ?: 'unknown');
```

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

### Limit Record Retrieval by Date Range

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Retrieve records within a specific date range by passing DateTimeInterface objects to the listRecords method. Use null for either the start or end date if only one boundary is needed.

```php
// Retrieve records from Jan 1, 2018 through October 1, 2018
$recs = $myEndpoint->listRecords('someMetaDataFormat', new 	DateTime('2018-01-01'), new 	DateTime('2018-10-01'));

foreach($recs as $rec) {
    var_dump($rec);
}
```

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

### Configure Guzzle v6 Client with Param Middleware

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Set up a Guzzle v6 client with the ParamMiddleware to automatically include specified query parameters in all requests. This involves creating a HandlerStack and pushing the middleware onto it.

```php
use Emarref\Guzzle\Middleware\ParamMiddleware
use GuzzleHttp\Client as GuzzleClient;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Middleware;
use Psr\Http\Message\RequestInterface;

// Setup the the Guzzle stack
$stack = HandlerStack()::create();
$stack->push(new ParamMiddleware(['api_key' => 'xyz123']));

// Setup Guzzle client, adapter, and PHP OAI-PMH client
$guzzleClient = new GuzzleClient(['handler' => $stack])
$guzzleAdapter = new \Phpoaipmh\HttpAdapter\GuzzleAdapter($guzzleClient)
$client  = new \Phpoaipmh\Client('http://some.service.com/oai', $guzzleAdapter);
```

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

### Configure Guzzle v6 Client with Retry Middleware

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Set up a Guzzle v6 client with the retry middleware for automatic rate limiting handling. This involves creating a HandlerStack and pushing the retry middleware factory onto it.

```php
use GuzzleRetry\GuzzleRetryMiddleware;
use GuzzleHttp\Client as GuzzleClient;
use GuzzleHttp\HandlerStack;

// Setup the the Guzzle client with the retry middleware
$stack = HandlerStack::create();
$stack->push(GuzzleRetryMiddleware::factory());
$guzzleClient = new GuzzleClient(['handler' => $stack]);

// Setup the Guzzle adpater and PHP OAI-PMH client
$guzzleAdapter = new \Phpoaipmh\HttpAdapter\GuzzleAdapter($guzzleClient);
$client  = new \Phpoaipmh\Client('http://some.service.com/oai', $guzzleAdapter);
```

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

### Customize Guzzle v6 Request Options

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Set default request options like connection and total timeout for Guzzle v6 client. Requires manual Guzzle client construction.

```php
use GuzzleHttp\Client as GuzzleClient;
use Phpoaipmh\Client;
use Phpoaipmh\Endpoint;
use Phpoaipmh\HttpAdapter\GuzzleAdapter;

$guzzle = new GuzzleAdapter(new GuzzleClient([
    'connect_timeout' => 2.0,
    'timeout'         => 10.0
]));

$myEndpoint = new Endpoint(new Client('http://some.service.com/oai', $guzzle));
```

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

### List Record Sets

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Iterate through all available record sets for an OAI-PMH endpoint by calling the listSets() method.

```php
foreach ($myEndpoint->listSets() as $set) {
    var_dump($set);
}
```

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

### Retrieve All Records

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Iterate through all records from an OAI-PMH endpoint for a specified metadata format. The iterator handles pagination and OAI-PMH logic automatically.

```php
// Recs will be an iterator of SimpleXMLElement objects
$recs = $myEndpoint->listRecords('someMetaDataFormat');

// The iterator will continue retrieving items across multiple HTTP requests.
// You can keep running this loop through the *entire* collection you
// are harvesting.  All OAI-PMH and HTTP pagination logic is hidden neatly
// behind the iterator API.
foreach($recs as $rec) {
    var_dump($rec);
}
```

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

### Customize Guzzle v5 Request Options

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Set default request options for Guzzle v5 by accessing the Guzzle client via the adapter and using setDefaultOption().

```php
use Phpoaipmh\Client,
    Phpoaipmh\HttpAdapter\GuzzleAdapter;

$adapter = new GuzzleAdapter();
$adapter->getGuzzleClient()->setDefaultOption('timeout', 120);
$client = new Client('http://some.service.com/oai', $adapter);

$myEndpoint = new Endpoint($client);
```

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

### Customize cURL Request Options

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Set cURL request options, such as timeout, by passing an array of key/value pairs to CurlAdapter::setCurlOpts().

```php
use Phpoaipmh\Client,
    Phpoaipmh\HttpAdapter\CurlAdapter;

$adapter = new CurlAdapter();
$adapter->setCurlOpts([CURLOPT_TIMEOUT => 120]);
$client = new Client('http://some.service.com/oai', $adapter);

$myEndpoint = new Endpoint($client);
```

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

### Send Arbitrary Query Parameters with Guzzle v5 Events

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Use Guzzle v5's event system to add arbitrary query parameters and headers to requests. This involves defining a listener function that modifies the request before it is sent.

```php
// Create a function or class to add parameters to a request
$addParamsListener = function(\GuzzleHttp\Event\BeforeEvent $event) {
   $req = $event->getRequest();
   $req->getQuery()->add('api_key', 'xyz123');

   // You could do other things to the request here, too, like adding a header..
   $req->addHeader('Some-Header', 'some-header-value');
};

// Manually create a Guzzle HTTP adapter
$guzzleAdapter = new \Phpoaipmh\HttpAdapter\GuzzleAdapter();
$guzzleAdapter->getGuzzleClient()->getEmitter()->on('before', $addParamsListener);

$client  = new \Phpoaipmh\Client('http://some.service.com/oai', $guzzleAdapter);
```

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

### Send Arbitrary Query Parameters with Phpoaipmh Client

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Send custom HTTP query parameters directly when making requests using the Phpoaipmh Client. This is useful for passing additional data not covered by standard OAI-PMH parameters.

```php
$client = new \Phpoaipmh\Client('http://some.service.com/oai');
$client->request('Identify', ['some' => 'extra-param']);
```

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

### Add Retry Subscriber for Guzzle v5

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Configure Guzzle v5 to use the Retry-Subscriber for handling rate limiting. This involves creating a RetrySubscriber instance and attaching it to the Guzzle client's emitter.

```php
// Create a Retry Guzzle Subscriber
$retrySubscriber = new \GuzzleHttp\Subscriber\Retry\RetrySubscriber([
    'delay' => function($numRetries, \GuzzleHttp\Event\AbstractTransferEvent $event) {
        $waitSecs = $event->getResponse()->getHeader('Retry-After') ?: '5';
        return ($waitSecs * 1000) + 1000; // wait one second longer than the server said to
    },
    'filter' => \GuzzleHttp\Subscriber\Retry\RetrySubscriber::createStatusFilter(),
]);

// Manually create a Guzzle HTTP adapter
$guzzleAdapter = new \Phpoaipmh\HttpAdapter\GuzzleAdapter();
$guzzleAdapter->getGuzzleClient()->getEmitter()->attach($retrySubscriber);

$client  = new \Phpoaipmh\Client('http://some.service.com/oai', $guzzleAdapter);
```

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

### Set Date Granularity Manually

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Manually set the date granularity for the OAI-PMH endpoint client by passing a Granularity constant to the Endpoint constructor. This overrides automatic detection.

```php
use Phpoaipmh\Client,
    Phpoaipmh\Endpoint,
    Phpoaipmh\Granularity;

$client = new Client('http://some.service.com/oai');
$myEndpoint = new Endpoint($client, Granularity::DATE_AND_TIME);
```

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

### Retrieve Records from a Specific Set

Source: https://github.com/caseyamcl/phpoaipmh/blob/master/README.md

Retrieve records from a specific set by providing the set name as the fourth argument to the listRecords method. This filters the results to only include records from the specified set.

```php
foreach ($myEndpoint->listRecords('someMetadataFormat', null, null, 'someSetName') as $record) {
    var_dump($record);
}
```

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