What bothers me is the return code
65280.
Unfortunately i am not sure what causes this, but it might be a faulty script ? Are you able to call it from the command line properly using
/usr/bin/php /home/bitcoin/script.php ?
You might try it with a simple shell script to see whether your php script is the reason or some configuration. Something like this should be enough:
#!/bin/bash
echo $(date +"%D - %H:%M:%S") >> /tmp/is_it_working
Place it anywhere and change walletnotify to:
walletnotify=/bin/bash /path/to/test.sh %s
See whether it can be called properly. If so, it should create a file in /tmp and the current time/date should be inside of the file.
If this dummy script is working, your script seems to be faulty. In this case post it somewhere so we can take a look at it. If you don't want to paste it publicly, feel free to PM it to me. I'll try to take a look at it.
If this dummy script isn't working either, some configuration is faulty, but currently not sure what exactly. Permissions maybe ?