PHP 7.0.6 Released

    The SplQueue class

    (PHP 5 >= 5.3.0, PHP 7)

    Introduction

    The SplQueue class provides the main functionalities of a queue implemented using a doubly linked list.

    Class synopsis

    SplQueue extends SplDoublyLinkedList implements Iterator , ArrayAccess , Countable {
    /* Methods */
    __construct ( void )
    mixed dequeue ( void )
    void enqueue ( mixed $value )
    void setIteratorMode ( int $mode )
    /* Inherited methods */
    public void SplDoublyLinkedList::add ( mixed $index , mixed $newval )
    public mixed SplDoublyLinkedList::bottom ( void )
    public int SplDoublyLinkedList::count ( void )
    public mixed SplDoublyLinkedList::current ( void )
    public int SplDoublyLinkedList::getIteratorMode ( void )
    public bool SplDoublyLinkedList::isEmpty ( void )
    public mixed SplDoublyLinkedList::key ( void )
    public void SplDoublyLinkedList::next ( void )
    public bool SplDoublyLinkedList::offsetExists ( mixed $index )
    public mixed SplDoublyLinkedList::offsetGet ( mixed $index )
    public void SplDoublyLinkedList::offsetSet ( mixed $index , mixed $newval )
    public void SplDoublyLinkedList::offsetUnset ( mixed $index )
    public mixed SplDoublyLinkedList::pop ( void )
    public void SplDoublyLinkedList::prev ( void )
    public void SplDoublyLinkedList::push ( mixed $value )
    public void SplDoublyLinkedList::rewind ( void )
    public string SplDoublyLinkedList::serialize ( void )
    public void SplDoublyLinkedList::setIteratorMode ( int $mode )
    public mixed SplDoublyLinkedList::shift ( void )
    public mixed SplDoublyLinkedList::top ( void )
    public void SplDoublyLinkedList::unserialize ( string $serialized )
    public void SplDoublyLinkedList::unshift ( mixed $value )
    public bool SplDoublyLinkedList::valid ( void )
    }

    Table of Contents

    User Contributed Notes

    Manu Manjunath
    2 years ago
    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().
    MrStonedOne
    1 year ago
    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;
            }
        }
    }
    ?>
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