SplMinHeap::compare

(PHP 5 >= 5.3.0, PHP 7)

SplMinHeap::compare — Compare elements in order to place them correctly in the heap while sifting up

protected int SplMinHeap::compare ( mixed $value1 , mixed $value2 )

Compare value1 with value2.

Result of the comparison, positive integer if value1 is lower 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.