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().
SplQueue 类
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
简介
SplQueue 类的主要功能是通过将迭代模式设置为 SplDoublyLinkedList::IT_MODE_FIFO 来提供使用双向链表实现的队列。
类摘要
/* 继承的常量 */
/* 方法 */
/* 继承的方法 */
}示例
示例 #1 SplQueue 示例
<?php
$q = new SplQueue();
$q[] = 1;
$q[] = 2;
$q[] = 3;
foreach ($q as $elem) {
echo $elem."\n";
}
?>以上示例会输出：
1 2 3
示例 #2 使用 SplQueue 高效处理任务
<?php
$q = new SplQueue();
$q->setIteratorMode(SplQueue::IT_MODE_DELETE);
// ... enqueue some tasks on the queue ...
// process them
foreach ($q as $task) {
// ... process $task ...
// add new tasks on the queue
$q[] = $newTask;
// ...
}
?>目录
- SplQueue::dequeue — Dequeues a node from the queue
- SplQueue::enqueue — Adds an element to the queue
add a note
User Contributed Notes 6 notes
Manu Manjunath ¶
10 years ago
mostefa dot medjahed dot pro at gmail dot com ¶
3 years ago
As was said before, the push () and pop () methods on a SplQueue object, its behave like a stack rather than a queue.
Knowing that the enqueue () and dequeue () methods are respectively aliases of push () and shift () methods, we can also use SplQueue :: push () and SplQueue :: shift () for the same purpose as SplQueue :: enqueue and SplQueue :: dequeue.
MrStonedOne ¶
9 years ago
You can use shift/unshift and push/pop to dequeue/undequeue and queue/unqueue respectively. Really handy for those applications that use sockets where you might not know you can't send data until you attempt to.
for example, this is a function for an application that will un-dequeue the remainder of the data if socket_write indicated it did not write the entire contents of the provided data.
<?php
function processSendQueue($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;
}
}
}
?>
lincoln dot du dot j at gmail dot com ¶
7 years ago
<?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);
$queue->dequeue(); //remove first one
print_r($queue);
?>
Output
A
B
C
SplQueue 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
)
)
Stingus ¶
8 years ago
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()); // false
var_dump(!$queue->isEmpty()); // true
booleantype at ya dot ru ¶
3 years ago
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().
