Just to save you some time.
Beware that octets in IP address are being treated as numbers. So, '10.0.0.11' is not equal to '10.0.0.011'. '011' is octal number (base 8), so it converts to '9'. You can even go further and see that '10.0.0.0xa' also works (equals to '10.0.0.16').
This is not PHP issue, though.