Linux – problem running script on receiving emai

I'm not quite sure what you are trying to do here. I'd suggest reading the CONTENT_FILTER_README and SMTPD_POLICY_README in the Postfix documentation. Your test.php script should probably be running as a content filter rather than a delivery-time script. Especially if you are using the script to reject messages based on sender/recipient, it's considered bad form to make those sorts of decisions after you've accepted the message for delivery.

The usual way to do content filtering in Postfix is for the front-end smtpd to hand off to a content filter via SMTP, LMTP or a pipe, and the content filter to reinject into an entry point that has no content filtering enabled -- either another smtpd with the content_filter parameter disabled in a -o override in master.cf, or local submission using /usr/sbin/sendmail with the Postfix pickup daemon's content_filter disabled in master.cf.

Since you are relaying to dovecot, is it possible you're trying to do the mysql mailbox method in dovecot where you don't have a physical home directory for the users? If that is the case, it appears your virtual transport isn't set up correctly.

The 1024 second delay looks curiously odd - almost as if postfix is not connecting to your server and timing out. I remember at one point postfix had an issue with localhost versus 127.0.0.1, and if you use 127.0.0.1, you need to make sure your database has given grants to dbuser@127.0.0.1.