PHP SplPriorityQueue compare() Function

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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.

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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