public function validate()
    {
        foreach (func_get_args() as $key) {
            $value = $this->parameters->get($key);
            if (! isset($value)) {
                throw new InvalidRequestException("The $key parameter is required");
            }
        }
    }
public function validate()
    {
        foreach (func_get_args() as $key) {
            $value = $this->parameters->get($key);
            if (! isset($value)) {
                throw new InvalidRequestException("The $key parameter is required");
            }
        }
    }
public function validate ( ) { foreach ( func_get_args ( ) as $ key ) { $ value = $ this -> parameters -> get ( $ key ) ; if ( ! isset ( $ value ) ) { throw new InvalidRequestException ( "The $key parameter is required" ) ; } } }
Validate the request.

This method is called internally by gateways to avoid wasting time with an API call
when the request is clearly invalid.

@param string ... a variable length list of required parameters
@throws InvalidRequestException
Validate the request .