public function pollLast()
    {
        if ($this->count() === 0) {
            return null;
        }

        $tail = $this[$this->tail];

        unset($this[$this->tail]);
        $this->tail--;

        return $tail;
    }
public function pollLast()
    {
        if ($this->count() === 0) {
            return null;
        }

        $tail = $this[$this->tail];

        unset($this[$this->tail]);
        $this->tail--;

        return $tail;
    }
public function pollLast ( ) { if ( $ this -> count ( ) === 0 ) { return null ; } $ tail = $ this [ $ this -> tail ] ; unset ( $ this [ $ this -> tail ] ) ; $ this -> tail -- ; return $ tail ; }
Retrieves and removes the tail of this queue, or returns `null` if this
queue is empty.

@return mixed|null the tail of this queue, or `null` if this queue is empty.

@see self::removeLast()
Retrieves and removes the tail of this queue or returns null if this queue is empty .