Quick and dirtyphp docblock based validation prototype...

validate_by_docblock

<?php

abstract class Validate 
{
	public abstract function isValid($value);
}

class ValidateInt extends Validate 
{
	public function isValid($value) 
	{
		return is_int($value);
	}
}

class ValidateString extends Validate 
{
	public function isValid($value) 
	{
		return is_string($value);
	}
}

class ValidateEMail extends Validate 
{
	public function isValid($value) 
	{
		return filter_var($value, FILTER_VALIDATE_EMAIL);
	}
}

class ValidateRequired extends Validate 
{
	public function isValid($value) 
	{
		return !empty($value) || $value == '0';
	}
}

class ValidatorFactory 
{
	/**
	 * @var Validate[] $validators
	 */
	protected $validators = array();

	/**
	 * @param string $className
	 * @return Validate
	 */
	public function get($className) 
	{
		if (!array_key_exists($className, $this->validators)) {
			$this->validators[$className] = new $className;
		}

		return $this->validators[$className];
	}
}

/**
 * Class AttributesTest
 */
class AttributesTest 
{
    /**
     * @param int $id
     * @validate ValidateInt, ValidateRequired
     */
	public $id = 1;

    /**
     * @param string $name
     * @validate ValidateString, ValidateRequired
     */
	public $name = 'Hans';

    /**
     * @param string $email
     * @validate ValidateEMail
     */
	public $email = 'hans@localhost';

	public $noValid;
}

function validate ($instance) 
{
	$reflection = new ReflectionClass(get_class($instance));
	$validatorFactory = new ValidatorFactory;

	foreach ($reflection->getProperties() as $property) {
		$docComment = $property->getDocComment();
		$docCommentLines = explode("\n", $docComment);

		foreach ($docCommentLines as $line) {
			if (strpos($line, '@validate') === false) {
				continue;
			}

			$validate = substr($line, strpos($line, '@validate') + 10);


			if (empty($validate)) {
				continue;
			}


			$validators = explode(',', $validate);

			foreach ($validators as $validator) {
				$validator = trim($validator);

                $propertyName = $property->name;
                var_dump($validator, $validatorFactory->get($validator)->isValid($instance->$propertyName));
			}
		}
	}
}

$inst = new AttributesTest;

validate($inst);