After iteration, the queue will be empty. Therefore, `count()` will return 0. You can circumvent this by iterating over a clone, instead of the actual queue.
https://stackoverflow.com/questions/27464012/splpriorityqueuenext-is-removing-the-item
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
SplPriorityQueue::count — Counts the number of elements in the queue
此函数没有参数。
Returns the number of elements in the queue.
After iteration, the queue will be empty. Therefore, `count()` will return 0. You can circumvent this by iterating over a clone, instead of the actual queue.
https://stackoverflow.com/questions/27464012/splpriorityqueuenext-is-removing-the-item