{
  "return_code":0,
  "return_message":"",
  "result":{
    "supported_carts_count":33,
    "supported_carts":[
      {
        "cart":[
          {
            "cart_id":"3DCartApi",
            "cart_name":"3DCart",
            "cart_versions":"",
            "params":[
              {
                "apiKey":null
              }
            ]
          },
          {
            "cart_id":"AceShop",
            "cart_name":"ACEShop",
            "cart_versions":"1.4.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"AspDotNetStorefront",
            "cart_name":"AspDotNetStorefront",
            "cart_versions":"8.x, 9.x",
            "params":[
              {
                "apiUser":null,
                "apiPass":null
              }
            ]
          },
          {
            "cart_id":"BigcommerceApi",
            "cart_name":"Bigcommerce",
            "cart_versions":"",
            "params":[
              {
                "ApiPath":null,
                "AdminAccount":null,
                "ApiKey":null
              }
            ]
          },
          {
            "cart_id":"Creloaded",
            "cart_name":"Loaded Commerce",
            "cart_versions":"",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Cscart",
            "cart_name":"CS-Cart",
            "cart_versions":"1.3.x - 3.0.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Cubecart",
            "cart_name":"CubeCart",
            "cart_versions":"3.x.x - 5.x.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Demandware",
            "cart_name":"Demandware",
            "cart_versions":"",
            "params":[
              {
                "storeId":null
              }
            ]
          },
          {
            "cart_id":"Interspire",
            "cart_name":"Interspire",
            "cart_versions":"3.x - 6.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"JooCart",
            "cart_name":"JooCart",
            "cart_versions":"1.5.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"LemonStand",
            "cart_name":"LemonStand",
            "cart_versions":"1.25",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Magento1212",
            "cart_name":"Magento",
            "cart_versions":"1.1.x - 1.9.x, 1.6.x - Enterprise",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"MagentoGo",
            "cart_name":"Magento Go",
            "cart_versions":"",
            "params":[
              {
                "apiUser":null,
                "apiKey":null
              }
            ]
          },
          {
            "cart_id":"MijoShop",
            "cart_name":"MijoShop",
            "cart_versions":"1.3.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"MobicartApi",
            "cart_name":"MobiCart",
            "cart_versions":"",
            "params":[
              {
                "userName":null,
                "apiKey":null
              }
            ]
          },
          {
            "cart_id":"Opencart14",
            "cart_name":"OpenCart",
            "cart_versions":"0.7.9 - 1.5.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Oscmax2",
            "cart_name":"osCMax",
            "cart_versions":"2.0.x - 2.5.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Oscommerce22ms2",
            "cart_name":"osCommerce",
            "cart_versions":"2.2.x, 2.3.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Pinnacle",
            "cart_name":"Pinnacle Cart",
            "cart_versions":"3.5.x - 3.7.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Prestashop",
            "cart_name":"PrestaShop",
            "cart_versions":"1.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"SSPremium",
            "cart_name":"Shop-Script Premium",
            "cart_versions":"2.8.x, 5.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Shopify",
            "cart_name":"Shopify",
            "cart_versions":"",
            "params":[
              {
                "apiKey":null,
                "apiPassword":null
              }
            ]
          },
          {
            "cart_id":"Shopware",
            "cart_name":"Shopware",
            "cart_versions":"",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Tomatocart",
            "cart_name":"TomatoCart",
            "cart_versions":"1.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Ubercart",
            "cart_name":"Ubercart",
            "cart_versions":"1.x - 2.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Virtuemart",
            "cart_name":"VirtueMart",
            "cart_versions":"1.0.x - 2.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Volusion",
            "cart_name":"Volusion",
            "cart_versions":"",
            "params":[
              {
                "Login":null,
                "EncryptedPassword":null
              }
            ]
          },
          {
            "cart_id":"WebAsyst",
            "cart_name":"WebAsyst Shop-Script",
            "cart_versions":"2.8.1 - 3.0.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Woocommerce",
            "cart_name":"WooCommerce",
            "cart_versions":"1.4.x - 2.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Xcart",
            "cart_name":"X-Cart",
            "cart_versions":"4.0.x - 4.5.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Xtcommerce",
            "cart_name":"xt:Commerce",
            "cart_versions":"3.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"XtcommerceVeyton",
            "cart_name":"xt:Commerce Veyton",
            "cart_versions":"4.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          },
          {
            "cart_id":"Zencart137",
            "cart_name":"Zen Cart",
            "cart_versions":"1.2.x, 1.3.x, 1.5.x",
            "params":[
              {
                "ftp_host":null,
                "ftp_port":null,
                "ftp_user":null,
                "ftp_password":null,
                "ftp_store_dir":null
              }
            ]
          }
        ]
      }
    ]
  }
}

index.php

<?php

include_once 'Connector.php';

$api = new Connector('PASTE_YOUR_API_KEY');

try {

  /**
   * Return stdClass
   */
  $result = $api->request('cart.list');

  echo "Supported cart count: " . $result->supported_carts_count . "\n";

  foreach($result->supported_carts[0]->cart as $cart) {

    echo "Cart ID: "       . $cart->cart_id       . "\n" .
         "Cart Name: "     . $cart->cart_name     . "\n" .
         "Cart Versions: " . $cart->cart_versions . "\n";

    echo "Params: \n";

    foreach($cart->params[0] as $name => $value) {
      echo " - " . $name . "\n";
    }

    echo "\n";

  }

} catch (Exception $e) {

  echo '#' . $e->getCode() . ' ' . $e->getMessage();

}

Connector.php

<?php

/**
 * Class Connector
 */
class Connector
{
  /**
   * URL to API API2Cart
   *
   * @var string A2C_URL
   */
  const A2C_URL = 'https://api.api2cart.com/v1.0/';

  /**
   * @var array $_params
   */
  private $_params = array();

  /**
   * @param string $apiKey
   * @param string $storeKey
   */
  public function __construct($apiKey, $storeKey = null)
  {
    $this->_params['api_key']   = $apiKey;

    if($storeKey !== null) {
      $this->_params['store_key'] = $storeKey;
    }
  }


  /**
   * Send request to API2Cart
   *
   * @param string $method Name method
   * @param array  $params List params for method
   *
   * @return stdClass
   *
   * @throws Exception
   */
  public function request($method, $params = array())
  {

    $params = array_merge($this->_params,$params);

    $ch = curl_init();

    $url = self::A2C_URL . $method . '.json?' . http_build_query($params);

    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
    curl_setopt($ch, CURLOPT_HEADER, false);
    curl_setopt($ch, CURLOPT_TIMEOUT, 300);
    curl_setopt($ch, CURLINFO_HEADER_OUT,true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_USERAGENT, 
      "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; " .
      "rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1");
    curl_setopt($ch, CURLOPT_HTTPHEADER, array (
      "Accept: */*",
    ));

    try {

      $response = trim(curl_exec($ch));

      if(curl_errno($ch) != CURLE_OK) {
        throw new Exception(curl_error($ch));
      }

      curl_close($ch);

      return $this->validate($response);

    } catch (Exception $e) {

      throw $e;

    }
  }

  /**
   * Validate received response
   *
   * @param string $response Response
   *
   * @return stdClass
   *
   * @throws Exception
   */
  private function validate($response)
  {
    $result = json_decode($response);

    if($result === null) {
      throw new Exception('Response NULL');
    }

    if($result->return_code != 0) {
      throw new Exception($result->return_message, $result->return_code);
    }

    return $result->result;
  }
}