public function setExtension( $extension )
    {
        if (strlen( $extension ) > 5) {
            throw new InvalidArgumentException( sprintf( 'Extension should be no longer than 5 characters (%s)',
                $extension ) );
        }

        $this->extension = $extension;

        return $this;
    }
public function setExtension( $extension )
    {
        if (strlen( $extension ) > 5) {
            throw new InvalidArgumentException( sprintf( 'Extension should be no longer than 5 characters (%s)',
                $extension ) );
        }

        $this->extension = $extension;

        return $this;
    }
@param  string $extension

@return $this