list.php

list.php

 <?php
 
 class MyList {
	private $list = array();
	
	public function __construct() {
		$this->list = func_get_args();
	}
 
	public function add($value) {
		$this->list[] = $value;
	}
 
	public function each($fn) {
		foreach($this->list as $current) {
			$fn($current);
		}
		
		return $this;
	}
	
	public function reduce($fn, $initialValue = null) {
		$this->each(function($current) use($fn, &$initialValue) {
			$initialValue = $fn($current);
		});
		
		return $initialValue;
	}
	
	public function filter($fn) {
		$list = new MyList;
		
		$this->reduce(function($current) use($fn, $list) {
			if($fn($current) === true) {
				$list->add($current);
			}
		});
		
		return $list;
	}
	
	public function toArray() {
		return $this->list;
	}
		
	public function debug() {
		echo '<pre>';
		print_r($this->toArray());
		echo '</pre>';
	}
 }
 
 $numbers = new MyList(1, 2, 3, 4, 5, 6);
 
 // 1 OK
$numbers->filter(function($value) {
	return $value% 2 === 0;
 })->debug();

 // 2 ERROR 
 function IS_EVEN($value) {
	return $value% 2 === 0;
} 

$numbers->filter(IS_EVEN)->debug();
  
 // 3 OK
$IS_EVEN = function($value) {
	return $value % 2 === 0;
};

$numbers->filter($IS_EVEN)->debug();