PHP SplPriorityQueue next() Function

<?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);

// Loop to print the priority
// queue elements
while($obj->valid()){
    
    // Print the current element
    echo $obj->current() . " ";
    
    // Move to next element of
    // priority queue
    $obj->next();
}

?>