Implementação de uma lista em PHP. Esta classe está pronta a usar. Permite aceder às duas extremidades da lista, bem como a qualquer outro ponto da lista, pelo que pode ser usada como pilha ou fila de espera.

<?php
/**
 ***************************
 * Author:  Carlos Correia *
 * Version: 0.1            *
 * Date:    06/11/2007     *
 ***************************
 */
class DefaultArray{
protected $array;
 
	/**
	 * Construct an empty array
	 */
	function __construct(){
		$this->array = array();
	}
 
	/**
	 * Add an element to the end of array
	 * @param object $element
	 */
	function addLast($element){
		$this->array[]=$element;
	}
 
	/**
	 * Add an element to the begin of array
	 * @param object $element
	 */
	function addFirst($element){
		array_unshift($this->array,$element);
	}
 
	/**
	 * Add element in array into position 
	 * indicate by the index argument
	 * @param int $index
	 * @param object $element
	 */
	function addElementAt($index,$element){
		if($index>=0 and $index<=count($this->array))
			array_splice($this->array,$index,0,$element);
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			if($index<0)
				throw new Exception('INDEX IS NEGATIVE');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * replace an element in array into position indicate
	 *  by the index argument
	 * @param int $index
	 * @param object $element
	 */
	function setElementAt($index,$element){
		if (isset($this->array[$index])) {
			$this->array[$index]=$element;
		}
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			if($index<0)
				throw new Exception('INDEX IS NEGATIVE');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * Return an element in array, indicate by the
	 * index argument
	 * @param int $index
	 * @return object
	 */
	function getElementAt($index){
 
		if(isset($this->array[$index]))
			return $this->array[$index];
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			if($index<0)
				throw new Exception('INDEX IS NEGATIVE');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * Return the first element in array
	 * @return object
	 */
	function getFirst(){
		if (isset($this->array[0]))
			return $this->array[0];
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * return the last element in array
	 * @return object
	 */
	function getLast(){
		$last_position=count($this->array)-1;
		if (isset($this->array[$last_position]))
			return $this->array[$last_position];
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			else
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * Remove the first element in array
	 * @return object
	 */
	function removeFirst(){
		if (isset($this->array[0])) 
			return array_shift($this->array);
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * Remove the last element in aray
	 * @return object
	 */
	function removeLast(){
		$last_position=count($this->array)-1;
		if ($last_position>=0)
			return array_pop($this->array);
 
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}
	}
 
	/**
	 * Remove an element in position indicate by 
	 * the index argument
	 * @param int $index
	 * @return removed element
	 */
	function removeElementAt($index){
		if(isset($this->array[$index])){
			$removed = array_splice($this->array,$index,1);
			return $removed[0];
		}
		else try {
			if(count($this->array)==0)	
				throw new Exception('EMPTY ARRAY');
			if($index<0)
				throw new Exception('INDEX IS NEGATIVE');
			else 
				throw new Exception('POSITION NOT FOUND');
			}catch (Exception $e){echo $e; exit;}	
	}
 
	/**
	 * Append currente array with other array
	 * given by argument
	 * @param DefaultArray or Array
	 */
	function appendArray($array){
		if (is_a($array,'DefaultArray')) 
			$this->array=array_merge($this->array,$array->getArray());
		elseif(is_array($array))
			$this->array=array_merge($this->array,$array);
		else try {
			throw new Exception('ARGUMENT IS INVALID');
		}catch (Exception $e){echo $e; exit;}
	}
 
	/**
	 * @return int size of array
	 */
	function getSize(){
		return count($this->array);
	}
 
	/**
	 * write a tree of values in array
	 * @return string
	 */
	function toString(){
		return var_export($this->array,true);
	}
 
	/**
	 * Return array
	 * @return array
	 */
	function getArray(){
		return $this->array;
	}
}
?>