Check your permissions and user, this error usually occurs when you do not have access.
Try PHP get_current_user() in your script to access the user you are accessing the script with.
Then if you have command line access (ssh) proceed to your script and perform:
This will list the file, its owner and its permissions. The owner or group of your script may not be accessible from the user on your android device. It may not be readable to others, something like: rwxrwx--- (the last 3 dashes represent access to other users other than the group and owner).
chmod a+r your-script.php
To change its permissions and give that a try. Let me know if you have a problems.