PHP Manual: Compare elements in order to place them correctly in the heap while sifting up.

Description

abstract protected int SplHeap::compare ( mixed $value1 , mixed $value2 )

Compare value1 with value2.

Warning

Throwing exceptions in SplHeap::compare can corrupt the Heap and place it in a blocked state. You can unblock it by calling SplHeap::recoverFromCorruption. However, some elements might not be placed correctly and it may hence break the heap-property.

Parameters

value1: The value of the first node being compared.
value2: The value of the second node being compared.

Return Values

Result of the comparison, positive integer if value1 is greater than value2, 0 if they are equal, negative integer otherwise.

Note:
Having multiple elements with the same value in a Heap is not recommended. They will end up in an arbitrary relative position.