Form Validation Call for help
My scriptygoddess crown to the first person that can give me the PHP code to validate a form field so that no special characters are allowed…
(well, okay it’s not really a crown; more like a plastic tiara… how about lots of plugs here, and the good feeling that you’ve helped out a friend in need?) 
UPDATE: Nevermind! I got it! (YAY! I get to keep my tiara!!) ;-P
(Update again: Actually, Amy saw my function and raised it… her’s is better/quicker/easier, etc.)
Amy is the grand champion Tiara holder!! 
Here’s a php function that will return true if the character is alphanumeric, and false if it’s anything else:
Here’s mine (Amy’s is better though…)
function noSpecialChars($string) {
$validate = true;
for ($i=0; $i < strlen($string); $i++) {
if (!ereg("[a-zA-Z0-9]", $string{$i})) {
$validate = false;
}
}
return $validate;
}
(so simple… yet, I will never admit to how many hours it took me to figure that damn thing out!!!)
Of course, what this function is doing is checking every single character… probably a bit of “server overhead” so if you have a simpler option… I’m all ears… well, eyes.
Here’s Amy’s:
function is_alphanumeric($test) {
return (preg_match(”/^[a-z0-9 ]+$/i”, $test));
}
September 16th, 2002 at 11:15 pm
(I’m not sure if this is helpful or not, but here’s what google found me!)
form validation
September 16th, 2002 at 11:17 pm
Oh, and maybe something to do with htmlspecialchars() ?
php.net - htmlspecialchars
September 16th, 2002 at 11:18 pm
Yeah, I saw that… and what he has there will validate that the string contains at least 1 alpha numeric character… but it could be mixed with special characters… I want to have it reject any and all special characters…
September 16th, 2002 at 11:22 pm
htmlscpecialchars() will translate special charcaters…
It’s probalby going to be some form of this function:
ereg() but the question is what do I put in there to deny all special characters…
September 17th, 2002 at 10:02 am
Oooh! Something I can help with!
function is_alphanumeric($test) {
return (preg_match(”/^[a-z0-9 ]+$/i”, $test));
}
Run it like this:
if ( !is_alphanumeric($submitted_variable) ) {
# fire error stuff
}
September 17th, 2002 at 10:14 am
Ok, when I tried those types of functions… it seemed to not catch it when it was a special character in the MIDDLE of alphanumeric characters.. it would only catch if it began or ended with a special character:
so:
3%2 would be acceptable
%32 would not be
32% would not be…
That’s why I got into the whole check every character thing…
September 17th, 2002 at 10:20 am
nope… my mistake. Yours works. Okay, you win the tiara!
But you have to explain to me why it works…
the difference between what you were doing with the preg_match, and what I was doing… is the last part… the “+$/i”… I had been using “+$/s” (which didn’t catch special charcters in the middle)
Can you tell me whats going on there? What does the “i” or “s” mean?
September 17th, 2002 at 10:53 am
I’d hang on to the tiara, Jenn. I didn’t write the function - many, many months ago I handed my first effort at it to Gareth, who patted me on the head and sent me back what you see here.
I pinged him and asked for an explanation that’s readable in English, and here’s his response:
“The $ matches the end of the line. The i is a flag meaning ‘case insensitive match.’ Likewise, the ^ at the beginning matches the beginning of the line. It won’t match (allow) any strings that contain spaces or whatever at the beginning/end.
“One could argue that you could use /^\w+$/ instead, but then it’d match (allow) the underscore character as well.”
Personally, I hate regexes. They drive me insane on a regular basis. I bribe Gareth with Reese’s Pieces (which are hard to get and expensive in Britain) to get help for regex issues like this.
September 17th, 2002 at 11:08 am
=sigh=
I still don’t get it…
Why would case have anything to do with it…
the only difference is that “i” vs. “s”
with “s”
3#3 is allowed
with “i”
3#3 is not
…duh… I’m so lost.
(Does he like Tiaras? LOL!)
I’ll send you some Reese’s Pieces to give to your friend…
December 8th, 2002 at 9:14 pm
I’ve been trying to figure this out forever too, and its really annoying, but here’s a function that seems to work perfectly, I got it from the user comments at php.net
http://www.php.net/manual/en/function.ereg.php
if (ereg(’^[[:alnum:]]+$’, $data)) {
echo ‘$data contains only letters and/or numbers’;
} else {
echo ‘$data contains characters other than letters and /or numbers.’;
}
and if you want to add characters to allow, like an underscore for instance, add a pipe and the _ after the [:alnum:], like so:
if (ereg(’^[[:alnum:]|_]+$’, $data)) {
echo ‘$data contains only letters and/or numbers’;
} else {
echo ‘$data contains characters other than letters and /or numbers.’;
}
hope that helps