PHP SPL Stack and Queue

dstest.php

<?php

//testing PHP Data Structures (SPL)

function displist($s){
   echo "<br>"; 
   $s->rewind(); 
   while($s->valid()){
    echo $s->current()." ";
    $s->next();
    }
}

$q = new SplStack();

$q[] = 1;
$q[] = 2;
$q[] = 3;
$q->push(4);
$q->add(4,5);

//View 
displist($q);
$q->pop();
displist($q);

$queue = new SplQueue();
$queue->enqueue('A');
$queue->enqueue('B');
$queue->enqueue('C');
$queue->enqueue('D');

//View 
displist($queue);
$queue->dequeue();
displist($queue);


?>