public function get_listener( $tag ) {
		return isset( $this->listeners[ $tag ] ) ? $this->listeners[ $tag ] : new Null_Listener();
	}
public function get_listener( $tag ) {
		return isset( $this->listeners[ $tag ] ) ? $this->listeners[ $tag ] : new Null_Listener();
	}
public function get_listener ( $ tag ) { return isset ( $ this -> listeners [ $ tag ] ) ? $ this -> listeners [ $ tag ] : new Null_Listener ( ) ; }
Get a listener for a certain tag.

@param string $tag

@return Listener|Null_Listener Null Listener is returned if listener for given tag does not exist.
Get a listener for a certain tag .