I need to execute a directory copy upon a user action, but the directories are quite large, so I would like to be able to perform such an action without the user being aware
If you are looking to execute a background process via PHP, pipe the command's output to /dev/null and add & to the end of the command.
/dev/null
&
exec("bg_process > /dev/null &");
Note that you can not utilize the $output parameter of exec() or else PHP will hang (probably until the process completes).
$output
exec()