Класс SplQueue

SplQueue inherits from SplDoublyLinkedList. So, objects of SplQueue support methods push() and pop(). But please be advised that if you use push() and pop() methods on a SplQueue object, it behaves like a stack rather than a queue.For example:$q = new SplQueue();$q->push(1);$q->push(2);$q->push(3);$q->pop();print_r($q);Above code returns:SplQueue Object(    [flags:SplDoublyLinkedList:private] => 4    [dllist:SplDoublyLinkedList:private] => Array        (            [0] => 1            [1] => 2        ))Note that 3 got popped and *not* 1.So, please make sure that you use only enqueue() and dequeue() methods on a SplQueue object and *not* push() and pop().

As was said before, the push () and pop () methods on a SplQueue object, its behave like a stack rather than a queue.Knowing that the enqueue () and dequeue () methods are respectively aliases of push () and shift () methods, we can also use SplQueue :: push () and SplQueue :: shift () for the same purpose as SplQueue :: enqueue and SplQueue :: dequeue.

You can use shift/unshift and push/pop to dequeue/undequeue and queue/unqueue respectively. Really handy for those applications that use sockets where you might not know you can't send data until you attempt to.

for example, this is a function for an application that will un-dequeue the remainder of the data if socket_write indicated it did not write the entire contents of the provided data.

<?php
function processSendQueue($socket, $sendQueue) {
    while (!$sendQueue->isEmpty()) {
                            //shift() is the same as dequeue()
        $senditem = $sendQueue->shift();

        //returns the number of bytes written.
        $rtn = socket_write($socket, $senditem);
        if ($rtn === false) {
            $sendQueue->unshift($senditem);
            throw new exception("send error: " . socket_last_error($socket));
            return;
        }
        if ($rtn < strlen($senditem) {
            $sendQueue->unshift(substr($senditem, $rtn);
            break;
        }
    }
}
?>

<?php  $queue = new SplQueue();$queue->enqueue('A');$queue->enqueue('B');$queue->enqueue('C');$queue->rewind();while($queue->valid()){    echo $queue->current(),"\n";    $queue->next();}print_r($queue);$queue->dequeue(); //remove first oneprint_r($queue);?>OutputABCSplQueue Object(    [flags:SplDoublyLinkedList:private] => 4    [dllist:SplDoublyLinkedList:private] => Array        (            [0] => A            [1] => B            [2] => C        ))SplQueue Object(    [flags:SplDoublyLinkedList:private] => 4    [dllist:SplDoublyLinkedList:private] => Array        (            [0] => B            [1] => C        ))

Take care that SplQueue::valid() is not returning true if the queue has nodes. Use isEmpty() instead:$queue = new SplQueue();$queue->enqueue('A');$queue->enqueue('B');$queue->enqueue('C');var_dump($queue->valid()); // falsevar_dump(!$queue->isEmpty()); // true

Answer to Manu Manjunath post (#114336).IMO, pop() works as expected.There are 2 main groups of methods:1) pop() & push() are inherited from SplDoublyLinkedList and can be applied to SplStack as well as SplQueue (ie are "faceless"). It isn't about stack or queue; it's just about deleting / adding element to the end of the list;2) the same situation with shift() & unshift(): it is just about adding an element to the beginning of the list, and doesn't matter, if we use it on SplStack or SplQueue.So, yes, $q->pop(); will remove *last* element from SplQueue $q.But enqueue() & dequeue() *are about* SplQueue. FIFO principle is realized by these methods, which were implemented *exactly* for queue purpose:- enqueue() adds an element to the end of the queue and is alias for "faceless" push() (FI...);- dequeue() removes element from the beginning of the queue and is alias for "faceless" shift() (...FO).If you want to delete *next in line* element from *queue*, use dequeue().If you want to delete *last* element from the list (doesn't matter, if it's queue or stack), use pop().