array's and testing field length's

troinfo

Hi,
I was wondering how I would setup an array to check each character in a string (on submit) such as a username to prevent invalid characters from going into the database.

Ex: testname is good
test`name is not good
testname's is not good

I'm new to php and the books I've read and other stuff on the web seem to only be concerned with the first and last character of a string.

any help or direction would be great.
Thanks,
PS this site is awesome for help 🙂

Anon

Let's say you only want letters, digits and maybe an underscore in $string.

The following preg_match() will return "true" if there's anything else in there and "false" otherwise:

preg_match('/[^{_a-zA-Z0-9]/',$string)}

Where the regexp means "anything that is not an underscore or a character in the ranges a to z, A to Z or 0 to 9". The whole thing between the [] is a "character class" and the ^ at the start supplies the "not".

If you want the reverse behaviour...

preg_match('/^{[_a-zA-Z0-9]*$/',$string)}

This time the ^ means "the start of the string", the $ means "the end of the string", and the * means "zero or more of the stuff preceding" - in this case a character class. This regexp succeeds on any string that consists entirely of underscores, letters, and digits. Literally it says "starting from the beginning, match zero or more underscores, letters, or digits, (and only underscores, letters or digits) right on to the end of the string".

Look up more on the regular expression functions. I personally prefer the preg_-named ones, but you might be happier with the ereg versions.

troinfo

ok i see what your saying.

I was trying this as a test

<?
if ($submit == submit){

$valid = "(reg("[a-z]",$field_name))";

for ($i = 1; $i < ($field_length); $i++) {

if ($field_name[$i] != $valid) {

$msg = "good";
} else {
$msg ="not good";
}
}
}
?>
<p><? "$msg"; ?>
<p>
<form method=post action="test.php" name=form>
<p> input test:<input type=text name=test size=25>
<p><input type=submit name=submit value=submit>
</form>

please try to hold back your laughter 😉
but this is what i was trying to do.

troinfo

could you tell me what i was doing wrong, if is it's not a bother.
thanks for all your help 🙂

Anon

I think you mean

<?
if ($submit == 'submit'){
if (preg_match("/^{[a-z]+$/",$test))} {
$msg = "good";
} else {
$msg ="not good";
}
}
?>

You want to allow upper case letters as well? Change the regexp to :/^[a-z]+$/i"