/**  
 * The Command abstraction.  
 * In this case the implementation must return a result,  
 * sometimes it only has side effects.  
 */ 
interface Validator  
{  
    /**  
     * The method could have any parameters.  
     * @param mixed  
     * @return boolean  
     */ 
    public function isValid($value);  
}  
 
/**  
 * ConcreteCommand.  
 */ 
class MoreThanZeroValidator implements Validator  
{  
    public function isValid($value)  
    {  
        return $value > 0;  
    }  
}  
 
/**  
 * ConcreteCommand.  
 */ 
class EvenValidator implements Validator  
{  
    public function isValid($value)  
    {  
        return $value % 2 == 0;  
    }  
}  
 
/**  
 * The Invoker. An implementation could store more than one  
 * Validator if needed.  
 */ 
class ArrayProcessor  
{  
    protected $_rule;  
 
    public function __construct (Validator $rule)  
    {  
        $this->_rule = $rule;  
    }  
 
    public function process(array $numbers)  
    {  
        foreach ($numbers as $n) {  
            if ($this->_rule->IsValid($n)) {  
                echo $n, "\n";  
            }  
        }  
    }  
}  
 
// Client code  
$processor = new ArrayProcessor(new EvenValidator());  
$processor->process(array(1, 20, 18, 5, 0, 31, 42));