#PriorityQueue

PriorityQueue.php

<?php

class PriorityQueue
{
    private $queue = [];

    public function enqueue($item, $priority)
    {
        $this->queue[] = [$item, $priority];
        $this->sort();
    }

    public function dequeue()
    {
        return array_shift($this->queue);
    }

    public function peek()
    {
        return $this->queue[0] ?? null;
    }

    public function isEmpty()
    {
        return empty($this->queue);
    }

    private function sort()
    {
        usort($this->queue, function ($a, $b){
            return $a[1] <=> $b[1];
        });
    }
}

$q = new PriorityQueue();

$q->enqueue('b', 1);
$q->enqueue('d', 3);
$q->enqueue('c', 2);
$q->enqueue('a', 0);

dump($q->dequeue());
dump($q->dequeue());
dump($q->dequeue());
dump($q->dequeue());