Posted by Philip Hallstrom on 04/29/05 19:08

> what kind of a function can I use that will tell me whether a variable is
> alphanumeric (that is has only characters A-Z or 1-9 )?

http://us3.php.net/manual/en/function.ctype-alnum.php

bool ctype_alnum ( string text )

Checks if all of the characters in the provided string, text, are
alphanumeric. In the standard C locale letters are just [A-Za-z] and the
function is equivalent to preg_match('/^[a-z0-9]*$/i', $text).

Returns TRUE if every character in text is either a letter or a digit,
FALSE otherwise.

----

Note that if you pass in an empty string you'll also get TRUE...

-philip

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