php object factory class

<?php
/**
 * 对象工厂
 * @author flynetcn
 */
class ObjectFactory
{
	private static $objSet = array();

	/**
	 * 清空工厂中的对象
	 */
	public function clear()
	{
		self::$objSet = array();
	}

	/**
	 * 在工厂中创建对象并将其返回
	 * 参数格式：$class_name, $class_param1, $class_param2, ...
	 */
	public static function create()
	{
		$argc = func_num_args();
		if ($argc <= 0) {
			throw new Exception(&#39;params error&#39;, 1);
		}
		$args = func_get_args();
		$class_name = array_shift($args);
		$params = $args;
		if (!$params) {
			$class_sign = $class_name;
		} else {
			$param_sign = serialize($params);
			if (strlen($param_sign) > 100) {
				$param_sign = md5($param_sign);
			}
			$class_sign = $class_name.'@'.$param_sign;
		}
		if (isset(self::$objSet[$class_sign])) {
			return self::$objSet[$class_sign];
		}
		$ref = new ReflectionClass($class_name);
		if ($ref->hasMethod('__construct') && !empty($params)) {
			$obj = $ref->newInstanceArgs($params);
		} else {
			$obj = $ref->newInstance();  
		}
		self::$objSet[$class_sign] = $obj;
		return $obj;
	}
}