Posted by trlists on 10/10/49 11:13

On 12 Apr 2005 blackwater dev wrote:

> $good = "joh_'";
>
> // Let's check the good e-mail
> if (preg_match("/[a-z0-9]/", $good)) {
> echo "Good";
> } else {
> echo "Bad";
> }
>
> This returns Good, why?

That regex matches any string which contains at least one (lowercase)
letter or one number somewhere within it. To match for only those
elements and no others you probably want:

if (preg_match("/^[a-z0-9]*$/", $good)) {

which will match a string which contains nothing but a-z and 0-9, and
will also match the empty string. See
http://www.php.net/manual/en/reference.pcre.pattern.syntax.php and look
at the meanings of ^, $, *, and +.

Other variations for the regex:

/^[a-z0-9]+$/ as above but will not match empty string
/^[a-z0-9]*$/i as above but matches upper case as well
/^[a-zA-Z0-9]*$/ like previous line -- as above but matches upper
case as well

As Chris S. pointed out, a regex is not needed for this task, so the
above is just academic.

--
Tom

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