public function addArgument($name, $value)
    {
        if (!isset($this->arguments[$name])) {
            $this->arguments[$name] = $value;
        }

        return $this;
    }
public function addArgument($name, $value)
    {
        if (!isset($this->arguments[$name])) {
            $this->arguments[$name] = $value;
        }

        return $this;
    }
public function addArgument ( $ name , $ value ) { if ( ! isset ( $ this -> arguments [ $ name ] ) ) { $ this -> arguments [ $ name ] = $ value ; } return $ this ; }
Add an event argument, only if it is not existing.

@param   string $name  The argument name.
@param   mixed  $value The argument value.

@return  Event  This method is chainable.

@since   2.0
Add an event argument only if it is not existing .