Absolutely not, at the very least double it and then add some more. Minimum wage would be £51.57 for those 9 hours! For a single days work, in isolation (not part of a longer contract or wage), £150+ is fine for a freelance PHP developer just starting out.
I think you have your answers, so I don't wish to repeat. However, was it case that you under-estimated the time the script was going to take? That is a common problem, but you'll learn to estimate the times to program scripts better as you become more acquainted with freelancing.
What I tended to do when freelancing was break all the items down into a list. Something like so:
Login -- 30 minutes;
Register -- 1 hour;
Profile -- 2 hours;
It will help you visualise the project, and therefore the duration you should expect it to take.
The man who comes back through the Door in the Wall will never be quite the same as the man who went out.
Also note, if something took say 6 hours because you were learning as you went along, obviously one cant charge the client for this. If this is the case, what I used to do is look back and see how long it would take me to do it now, now that I know how and charge accordingly.
A balance must be found, if one charges too low, to increase the chances of repeat business, next time round the client expects the same low rate.