[SOLVED] Username check

[Agum]

I need a RegEx pattern that checks for usernames.

The username must consist of only alphanumeric characters or hyphen (-) or underscore (_).

The thing is, hyphen or underscore must have an alphanumeric character before and after it.

 

Test cases:

Spiderman = ok

Spider-man = ok

Spider_man = ok

Spider--man = err

Spider__man = err

-Spiderman = err

Spiderman_ = err

Spider-man-2 = ok

1_Spider-man = ok

 

me and my friend came up with two different ways to do this:

^[a-zA-Z0-9]+([-_][a-zA-Z0-9]+)*$

matches the "good" stuff (return true on OK, return false on ERR)

^[-_]|[^a-zA-Z0-9-_]|(--)|(-_)|(_-)|(__)|[-_]$

matches the "bad" stuff (return true on ERR, return false on OK)

 

which one would be more efficient? if they are both pretty bad, do you have a suggestion for a better way to do this?

 

also, what's the difference between preg and ereg in php? which one do you recommend and why?

[monk.e.boy]

why is 'spider--man' and error?

 

Why not forget regex and just look for illegal characters, if '-' is illegal, then trow out 'spider-man' if '-' is legal then 'po---------ooo' is legal.

 

is 'jooooooooohn' legal? how about 'jo------oooooo----n'?

 

I think your logic is a bit wonky.

 

monk.e.boy

[Wildbug]

Since your undesireable characteristics are so well defined, I would go with the regex that matches what you DON'T want.  No beginning hyphen/underscore, no double hyphen/underscore, no non-word/non-hyphen characters, no ending hyphen/underscore.

 

<?php
$usernames = array(
'Spiderman',
'Spider-man',
'Spider_man',
'Spider--man',
'Spider__man',
'-Spiderman',
'Spiderman_',
'Spider-man-2',
'1_Spider-man',
'Spider & Man'
);

foreach ($usernames as $uname) echo $uname . (preg_match('/^[-_]|[-_]{2,}|[^\w-]|[-_]$/',$uname) ? " fails\n" : " is acceptable\n");
?>

Spiderman is acceptable
Spider-man is acceptable
Spider_man is acceptable
Spider--man fails
Spider__man fails
-Spiderman fails
Spiderman_ fails
Spider-man-2 is acceptable
1_Spider-man is acceptable
Spider & Man fails

 

I'm guessing you'll only be using this comparison when a new user is registering a new username, right?  This will be plenty fast for that occasion.  If you were creating a program that had to plow through thousands of names very often (i.e., performance was paramount), a more efficient way to do this would probably be to split up the conditions and string them together with ORs.  That way as soon as a failure is encountered, execution moves on.  But that's just academic, using the method above will work fine.

 

As far as preg vs. ereg, I personally prefer the preg* functions if only because I learned regular expressions when learning Perl.  I think there are some extensions to the Perl-style syntax that give them more power than the POSIX ones.  I don't know about speed/efficiency, however.  There are some comparisons and caveats in the manual for both of these.

[Agum]

thanks Wildbug.

that's a good point - since it only needs to run at account sign-up, I guess it's ok even if it's a bit unefficient.

 

mon.e.boy,

if you have played WoW, you will know that character names allow 1 hyphen, and it cannot be in the first or last char, and you cannot have 2 hyphens consecutively. my sytem has similar rules except a few differences, such as allowing underscore, etc.

 

* how do I mark this thread as SOLVED and change the icon?

[Wildbug]

I think the topic solved link is at the bottom of your thread.

[satant]

why u make all of that i think u only need to writ the unacceaptaple leteers