<?php
class ReadingList
{
    protected $stack;
    protected $limit;
    public function __construct($limit = 10) {
        $this->stack = array();
        $this->limit = $limit; }
    public function push($item) {
        if (count($this->stack) < $this->limit) {
            array_unshift($this->stack, $item); } else {
            throw new RunTimeException('Stack is full!'); }
    }
    public function pop() {
        if ($this->isEmpty()) {
          throw new RunTimeException('Stack is empty!');
      } else {
            return array_shift($this->stack); }
    }
    public function top() {
        return current($this->stack); }
    public function isEmpty() {
        return empty($this->stack); }
}
$stack = new ReadingList();
	$stack -> push ();
	 $stack -> push ();
	$stack -> push ();
	$stack -> push ();
 
echo $stack -> isEmpty ();

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