[Zapatista]

I'm creating a log in/registration on a site I'm making and I want to limit what the people use as their usernames and I know you have to you ereg() but I'm not sure how and I've looked at 2 books and the PHP's official website and I've still got nothing. I want it to allow all letters, numbers, and dashes but nothing else. Please help, I'm stuck.

[kvnband]

I'm still learning regular expressions, but I know that

Code:

^[a-zA-Z0-9]$

is for a-z, A-Z, 0-9 but I'm not sure how you add a hyphen in there.

[Keith]

To allow upper & lowercase letters, numbers, spaces, hyphens, underscores, and periods, I use:

PHP Code:

ereg_replace("[^A-z0-9 _-.]", "", $username); 

Any characters other than those will be stripped.

[kvnband]

Cool...I didn't know if you could add things like hyphens, etc... right in there or not. (I was wondering because of A-z I thought maybe php would get confused if I added a hyphen)

Kevin

[Keith]

Yeah, took me a bit to discover that... just start adding them at the end.

[Zapatista]

thanks for all of your help

[Zapatista]

I tried what you suggested and it still won't work. It only works if I just put in a single character. Anymore than that will result in it not matching. Any suggestions?

[mikaelf]

Originally Posted by kvnband

I'm still learning regular expressions, but I know that

Code:

^[a-zA-Z0-9]$

is for a-z, A-Z, 0-9 but I'm not sure how you add a hyphen in there.

What's wrong with above code:
^[a-zA-Z0-9]$ -> will only evalute true for single character not many.

Originally Posted by keith

To allow upper & lowercase letters, numbers, spaces, hyphens, underscores, and periods, I use:

PHP Code:

ereg_replace("[^A-z0-9 _-.]", "", $username); 



Any characters other than those will be stripped. 

What's wrong with above code:
1. A-z should be A-Z or a-z
2. The operator ^ in square bracket [] will behave as negation and not assertion. Thus ^A-Z means you disallow alphabet A through Z
3. The dot (.) refers to all characters except newline, if you want to include the dot itself, cast it first using \
4. As with kvnband, the regex will only evaluate single character.

Valid regular expression should be:
$isMatch = preg_match('/^[a-zA-Z_-\.]+$/',$username);
or
$isMatch = preg_match('/^[a-z_-\.]+$/i',$username);
or
$isMatch = preg_match('/^[a-z_\-\.]+$/i',$username); //safely cast dash

Notes:
1.It's much better to use preg_match than ereg because it will evaluate faster (you may give a try for speed test)
2.Before using the regex test function, trim the trailing spaces by using php function trim()