### Install Verotel FlexPay PHP Client via Composer

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Instructions for adding the Verotel FlexPay PHP client library to a project using Composer, the PHP dependency manager.

```bash
composer require verotel/flexpay-php-client
```

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

### Include Composer Autoloader in PHP

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Demonstrates how to include Composer's autoloader in a PHP project, essential for using classes from installed dependencies like the FlexPay client.

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

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

### Validate Verotel FlexPay Postback Signature

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Provides an example of validating incoming postback parameters from Verotel FlexPay using the client's validate_signature method. It checks the integrity of the data and handles invalid signatures by sending an HTTP 500 error.

```php
if (!$flexpayClient->validate_signature($_GET)){
    http_response_code(500);
    echo "ERROR - Invalid signature!";
    exit;
}

// handle correct postback
...

echo "OK";
```

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

### Construct Verotel FlexPay Client Instance

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Illustrates how to initialize the Verotel FlexPay client. This involves creating a Brand instance using a merchant ID and then instantiating the Client with a shop ID, signature key, and the brand object.

```php
// get your brand instance
$brand = Verotel\FlexPay\Brand::create_from_merchant_id(/* Your customer ID */ '9804000000000000');

$flexpayClient = new Verotel\FlexPay\Client(/* shop ID */ 12345, "FlexPay Signature Key", $brand);
```

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

### Directly Include Verotel FlexPay Client in PHP

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Shows how to manually include the Verotel FlexPay Client class file in a PHP project without using Composer, specifying the direct path to the source file.

```php
require_once '<path-to-flexpay-php-client>/src/Verotel/FlexPay/Client.php';
```

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

### Generate Verotel FlexPay Purchase URL

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Demonstrates how to obtain a payment URL for a new purchase using the FlexPay client. It requires an array of parameters including priceAmount, priceCurrency, and description to define the transaction.

```php
$purchaseUrl = $flexpayClient->get_purchase_URL([
    "priceAmount" => 2.64,
    "priceCurrency" => "EUR",
    "description" => "Test purchase",
]);
```

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

### Generate Verotel FlexPay Cancel Subscription URL

Source: https://github.com/verotel/flexpay-php-client/blob/master/README.md

Shows how to generate a URL for cancelling an existing subscription via the FlexPay client. This method requires the saleID of the subscription to be cancelled.

```php
$cancelUrl = $flexpayClient->get_cancel_subscription_URL([ "saleID" => 12345 ]);
```

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