SplPriorityQueue::compare Compare priorities in order to place elements correctly in the heap while sifting up &reftitle.description; public intSplPriorityQueue::compare mixedpriority1 mixedpriority2 Compare priority1 with priority2. &reftitle.parameters; priority1 The priority of the first node being compared. priority2 The priority of the second node being compared. &reftitle.returnvalues; Result of the comparison, positive integer if priority1 is greater than priority2, 0 if they are equal, negative integer otherwise. Multiple elements with the same priority will get dequeued in no particular order.