PMA\libraries\DatabaseInterface::checkDbExtension PHP Method

    public static function checkDbExtension($extension = 'mysql')
    {
        if (function_exists($extension . '_connect')) {
            return true;
        }
        return false;
    }

 /**
  * Test database connection
  *
  * @param string $connect_type 'tcp' or 'socket'
  * @param string $host         host name
  * @param string $port         tcp port to use
  * @param string $socket       socket to use
  * @param string $user         username to use
  * @param string $pass         password to use
  * @param string $error_key    key to use in return array
  *
  * @return bool|array
  */
 public static function testDBConnection($connect_type, $host, $port, $socket, $user, $pass = null, $error_key = 'Server')
 {
     //    static::testPHPErrorMsg();
     $error = null;
     $host = PMA_sanitizeMySQLHost($host);
     if (DatabaseInterface::checkDbExtension('mysqli')) {
         $socket = empty($socket) || $connect_type == 'tcp' ? null : $socket;
         $port = empty($port) || $connect_type == 'socket' ? null : $port;
         $extension = 'mysqli';
     } else {
         $socket = empty($socket) || $connect_type == 'tcp' ? null : ':' . ($socket[0] == '/' ? '' : '/') . $socket;
         $port = empty($port) || $connect_type == 'socket' ? null : ':' . $port;
         $extension = 'mysql';
     }
     if ($extension == 'mysql') {
         $conn = @mysql_connect($host . $port . $socket, $user, $pass);
         if (!$conn) {
             $error = __('Could not connect to the database server!');
         } else {
             mysql_close($conn);
         }
     } else {
         $conn = @mysqli_connect($host, $user, $pass, null, $port, $socket);
         if (!$conn) {
             $error = __('Could not connect to the database server!');
         } else {
             mysqli_close($conn);
         }
     }
     //    static::testPHPErrorMsg(false);
     if (isset($php_errormsg)) {
         $error .= " - {$php_errormsg}";
     }
     return is_null($error) ? true : array($error_key => $error);
 }