Configure Postfix with Virtual Mailboxes to forwar

Question

I am using the Postfix MTA with a virtual configuration from MySQL for the Users and Forwardings. Now I want some Adresses (that are dynamicaly generated, for writing via E-Mail to a Forum) to be forwarded to a php-script.

I already have tried to put the script quoted and piped as destination bit it doesn't work. "|php -q /path/to/script.php" But if I send a mail to that domain it says: User “|php -q /path/to/script.php"@mydomain.tld not found