Call another PHP script and return control to user before the other script completes

Question

I'm actually trying to apply this to a script that sends email. The sending email part takes a few seconds which is too long. What I want is for the first script to do its stuff and trigger another script (which sends the Email), but I want the first script to return control to the user without waiting for the second script to send the email.

Options that I have considered:
Cron Job: For this I'll have to have a cron job run something like every 2 mins. Not feasible!
PHP script activating a cron job which deactivates itself when done: Well ok, but how do I do this? Can PHP do this?

Answer 1

You can also call the shell and manually call the PHP file. No cron required and no waiting.

http://www.php.net/manual/en/function.exec.php

From the Notes Section

"If a program is started with this function, in order for it to continue running in the background, the output of the program must be redirected to a file or another output stream. Failing to do so will cause PHP to hang until the execution of the program ends."