The strategy pattern using PHP

In the strategy pattern, algorithms are extracted from complex classes so they can be replaced easily. For example, the strategy pattern is an option if you want to change the way pages are ranked in a search engine. Think about a search engine in several parts -- one that iterates through the pages, one that ranks each page, and another that orders the results based on the rank. In a complex example, all those parts would be in the same class. Using the strategy pattern, you take the ranking portion and put it into another class so you can change how pages are ranked without interfering with the rest of the search engine code.
As a simpler example, Strategy.php shows a user list class that provides a method for finding a set of users based on a plug-and-play set of strategies.

Strategy.php

<?php
interface IStrategy {
function filter($record);
}

class FindAfterStrategy implements IStrategy {
private $_name;

public function __construct($name) {
$this->_name = $name;
}

public function filter($record) {
return strcmp($this->_name, $record) <= 0;     } }  class RandomStrategy implements IStrategy {     public function filter($record) {         return rand(0, 1) >= 0.5;
}
}

class UserList {
private $_list = array();

public function __construct($names) {
if ($names != null) {
foreach($names as $name) {
$this->_list []= $name;
}
}
}

public function add($name) {
$this->_list []= $name;
}

public function find($filter) {
$recs = array();
foreach($this->_list as $user) {
if ($filter->filter($user))
$recs []= $user;
}
return $recs;
}
}

$ul = new UserList(array("Andy", "Jack", "Lori", "Megan"));
$f1 = $ul->find( new FindAfterStrategy("J") );
print_r($f1);

$f2 = $ul->find(new RandomStrategy());
print_r($f2);
?>