SplPriorityQueue
PHP Manual

SplPriorityQueue::compare

Compare priorities in order to place elements correctly in the heap while sifting up.

Description

public int SplPriorityQueue::compare ( mixed $priority1 , mixed $priority2 )

Compare priority1 with priority2.

Parameters

priority1

The priority of the first node being compared.

priority2

The priority of the second node being compared.

Return Values

Result of the comparison, positive integer if priority1 is greater than priority2, 0 if they are equal, negative integer otherwise.

Note:

Multiple elements with the same priority will get dequeued in no particular order.