The strtoupper function returns nothing on the following:

PAris

but works on:

\"PAris\" 
PARis
Paris

and anything else.

The script I used to find this is:

// Make the suburb all upper case
$SB = strtoupper($SB);
echo $SB;

I haven't really got the time to look at the source code so I'll just use strtr in the meantime.