MySQL Count Results trap needed

[HotShot99]

OK, so this is complex (for me) so I'll try and keep it simple.

I have a PHP script interacting with MySQL.
The page allocates stock, multiple users could (theoretically) try to allocate ONE stock item at the same time.
Thus I have managed to add a WHERE clause to ensure this can't happen.

So,
if it has NOT been allocated yet, the UPDATE sql works fine.
if it HAS been allocated yet, the UPDATE sql works fine.

BUT...it doesn't inform the user when it fails to update the DB - how do I check how if the UPDATE sql has altered 1 or 0 records?

Thanks in advance,
C

[HotShot99]

Found it...

For counting the number of UPDATE, DELETE, INSERT or REPLACE records:
mysql_affected_rows()

For counting the number of SELECT query records:
mysql_num_rows()

C