protected function helper($helperName)
    {
        if (!isset($this->helpers[$helperName])) {
            throw new \InvalidArgumentException('Unable to locate controller helper: ' . $helperName);
        }

        return $this->helpers[$helperName];
    }
protected function helper($helperName)
    {
        if (!isset($this->helpers[$helperName])) {
            throw new \InvalidArgumentException('Unable to locate controller helper: ' . $helperName);
        }

        return $this->helpers[$helperName];
    }
protected function helper ( $ helperName ) { if ( ! isset ( $ this -> helpers [ $ helperName ] ) ) { throw new \ InvalidArgumentException ( 'Unable to locate controller helper: ' . $ helperName ) ; } return $ this -> helpers [ $ helperName ] ; }
Obtain a controller helper by its key name.

@param string $helperName

@throws \InvalidArgumentException

@return mixed
Obtain a controller helper by its key name .