It appears that the script requires a terminal input at some point. That causes it to stop until it is put in the foreground again, and some reply given.
If you have no reply (such as a default "y" or just a return) you may be out of luck. If you do have something to input, put it in a file and redirect stdin from that file:
$ php -f file.php 2>&1 > file.txt <your-input-file &