The SplPriorityQueue::compare() function is an inbuilt function in PHP which is used to compare the priority queue elements to place at a particular order in the heap data structure.
Syntax:
int SplPriorityQueue::compare(
mixed $priority1 , mixed $priority2 )
Parameters: This function accepts two parameters as mentioned above and described below:
- priority1: This parameter holds the priority of the first node that is  being compared.
- priority2: This parameter holds the priority of the second node that is  being compared.
Return Value: This function returns the result of the comparison function. It returns +ve integer if priority1 is greater than priority2, 0 if both are equal and -ve integer otherwise.Â
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Example:
PHP
<?php   // Declare a class class priorityQueue extends SplPriorityQueue {           // Compare function to compare priority     // queue elements     public function compare($p1, $p2) {         if ($p1 === $p2) return 0;         return $p1 < $p2 ? -1 : 1;     } }   // Create an object of priority queue $obj = new priorityQueue();   // Insert elements into the queue $obj->insert("Geeks",2); $obj->insert("GFG",1); $obj->insert("G4G",3); $obj->insert('G',4);   // Display the priority queue elements var_dump($obj);   ?> |
Output
object(priorityQueue)#1 (3) {
["flags":"SplPriorityQueue":private]=>
int(1)
["isCorrupted":"SplPriorityQueue":private]=>
bool(false)
["heap":"SplPriorityQueue":private]=>
array(4) {
[0]=>
array(2) {
["data"]=>
string(1) "G"
["priority"]=>
int(4)
}
[1]=>
array(2) {
["data"]=>
string(3) "G4G"
["priority"]=>
int(3)
}
[2]=>
array(2) {
["data"]=>
string(5) "Geeks"
["priority"]=>
int(2)
}
[3]=>
array(2) {
["data"]=>
string(3) "GFG"
["priority"]=>
int(1)
}
}
}
Reference: https://www.php.net/manual/en/splpriorityqueue.compare.php
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