Not Allowing Symbols In A String

galexcd

Jul 26 2006, 05:34 AM

I was looking for a quick solution so i could check a string for any symbols and stuff (basically anything that isnt numbers and letters) in it. One of the first google searches that came up were for a forum called "sitepoint". The thread was talking about the same thing I was trying to do.

This was their solution:

CODE

if (ereg("[a-zA-Z0-9]+", $username)) {
echo 'OK.';
} else {
echo 'Invalid characters.';
}

So i tried it out. Didn't work. I played with the code and i still couldn't get it to work... So I did what i didn't want to do: do it my way. Heres what i coded:

CODE

$allowed="q,w,e,r,t,y,u,i,o,p,a,s,d,f,g,h,j,k,l,z,x,c,v,b,n,m,Q,W,E,R,T,Y,U,I,O,P,A,S,
D,F,G,H,J,K,L,Z,X,C,V,B,N,M,1,2,3,4,5,6,7,8,9,0,-,_";
if(str_replace(explode(",",$allowed),"",$username)=="")
{
//OK
}else{
//contains symbols
}

Almost everything I code is very crude and I'm sure this could have been done with 1 simple function, but oh well. My way works fine.
---------
Heres the link to the thread if anybody is interested: http://www.sitepoint.com/forums/showthread.php?t=65200
--------
So why did i post this?
Basically The only reason i posted it here is for input. Even though i dont really need it now, anybody know why the original code didn't work? How about some input for the code i came up with! hehe

. Maby sombody could use my code?
I donno. Since i just signed up to that forum just to make that one reply, I wont be visiting them again for a responce, so i just moved the whole issue over here, so I could get other people's oppinion.... Ok I think i should stop talking now.

Reply

truefusion

Jul 26 2006, 05:31 PM

Well, the first code provided wouldn't have worked if there was an underscore, or a hyphen in the username. But it should have worked if it only contained letters and/or numbers.

But the simpler way to go about it for your second code would have been:

CODE

if (ereg('[\\w-]+', $username)) {
echo "OK";
} else {
echo "Invalid Characters, or no username provided.";
}

Reply

galexcd

Jul 29 2006, 11:55 PM

QUOTE(truefusion @ Jul 26 2006, 10:31 AM)

Well, the first code provided wouldn't have worked if there was an underscore, or a hyphen in the username. But it should have worked if it only contained letters and/or numbers.

But the simpler way to go about it for your second code would have been:

CODE

if (ereg('[\\w-]+', $username)) {
echo "OK";
} else {
echo "Invalid Characters, or no username provided.";
}

the first one din't work though, it was compleatly screwed up. $*%username said "invalid characters" but username$*% was allowed. Thats what made me finaly break down and drop the ereg function

Reply

Spectre

Jul 30 2006, 06:28 AM

Try inversing the original regular expression, so that it scans for any characters which are not in the given set (in this case, anything that is not alphanumeric):

CODE

if (ereg('[^a-zA-Z0-9]', $username)) {
echo 'Invalid characters.';
} else {
echo 'OK.';
}

You can always add to the set to include other characters you want to allow, such as hyphens/dashes and underscores:

CODE

[^a-zA-Z0-9\-_]

The problem with the original expression is that it was matching any string that contained a consecutive set of alphanumeric characters at the start of the string. If any other characters followed, it simply ignored them, but still matched the expression.

Reply

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