How to detect syntax errors before releasing a PHP application?

Hi all, When I write Java-based applications, I can compile JSP pages to detects syntax errors before releasing the applications. I'm wondering if there is some tool like that in PHP writing? Of course PHP pages cannot be compiled like JSP pages because PHP is an interpreted language. But it would be great to have some tool to check PHP syntax of an PHP application (detects missing ";","}",...). I know that PHP engine has an internal parser. Can we use it to check our code without requesting every PHP pages? Or anyone knows about some similar tool to check PHP error? Or we should write an simple PHP parser? :) I have used Zend Safeguard Suite to detect PHP errors but I don't want to buy it. I need something free. Thanks. Regards, Thai