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Matthew Weier O'Phinney's Blog: Taming SplPriorityQueue

Note: This article was originally published at PHPDeveloper on 19 January 2011.
PHPDeveloper

Matthew Weier O'Phinney has a new post to his blog today looking at one of the tools the Standard PHP Library (SPL) has to offer developers - the SplPriorityQueue (PHP 5.3+)

SplPriorityQueue is a fantastic new feature of PHP 5.3. However, in trying to utilize it in a few projects recently, I've run into some behavior that's (a) non-intuitive, and (b) in some cases at least, undesired. In this post, I'll present my solutions.

He talks about the "first in, first out" nature of queues and how it differs from a stack (including links to some of the other SPL offerings for both). He then moves into the problems he was seeing - that iteration removes values from the heap and the unexpected order of equal values in the queue. To solve the first problem, he creates an "outer iterator" that creates an "innerQueue" that's protected. The solution for the second issue - the random queue order - is a simple one: priority indexes aren't required to be integers. Strings can be substituted to help make things a bit more unique.