gistfile1.php[345]

<?php 

class Link {
	public $key;
	public $value;
	public $next = null;	

	public function __construct($key, $value) {
		$this->key = $key;
		$this->value = $value;	
	}

	public function displayLink() {
		echo '{'.$this->key.' : '.$this->value.'} ';
	}
}

class LinkList {
	private $first = null;

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

	public function insertFirst($key, $value) {
		$link = new Link($key, $value);		
		
		if (!$this->isEmpty()) {
			$link->next = $this->first;	
		}

		$this->first = $link;
	}

	public function deleteFirst() {
		if ($this->isEmpty()) {
			return null;
		}

		$this->first = $this->first->next;

		return $this->first;
	}

	public function displayList() {
		if ($this->isEmpty()) {
			echo 'LinkList is null'; 	
			return ; 
		}

		$current = $this->first;
		while ($current !== null) {
			$current->displayLink();	

			$current = $current->next;
		}
	}	

}

$linkList = new LinkList();
$linkList->insertFirst(1, 1.99);
$linkList->insertFirst(2, 2.99);
$linkList->insertFirst(3, 3.99);
$linkList->insertFirst(4, 4.99);

$linkList->displayList();
echo "\n";

$linkList->deleteFirst();
$linkList->displayList();
echo "\n";

$linkList->deleteFirst();
$linkList->displayList();

?>