(PHP 5 >= 5.3.0, PHP 7)
SplHeap::compare — Compare elements in order to place them correctly in the heap while sifting up.
Compare value1 with value2.
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.
value1The value of the first node being compared.
value2The value of the second node being compared.
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.