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

		$current = $this->first;
		while ($current !== null) {
			if ($current->key == $key) {
				return $current;
			} else {
				$current = $current.next;
			}
			
		}

		return null;
	}

	public function delete($key) {
		$current = $this->first;
		$previous = $this->first;

		while ($current->key != $key) {
			if ($current->next == null) {
				return null;
			} else {
				$previous = $current;
				$current = $current->next;
			}
		}

		if ($current == $this->first) {
			$this->first = $this->first->next;
		} else {
			$previous->next = $current->next;
		}

		return current;
	}

}

$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();

//$linkList->find(4)->displayLink();
//$linkList->find(5)->displayLink();
$linkList->delete(4);
$linkList->displayList();
echo "\n";
$linkList->delete(3);
$linkList->displayList();
echo "\n";


?>