String checking with PHP

[buanzox () USA NET (Arturo Busleiman)]

(Version en espa~nol, leer mas abajo)

Well, yesterday I asked for help regarding how to check if a string has
only valid characters, well here I attach what I programed by myself, I
hope it is useful for everyone out there who needs it. It's really simple,
and if you experts find any bug or problem (exceptuating speed :), PLEASE
mail me.

=-=-=

Bueno, lo siguiente es una funcioncita que escribi en PHP que lo que hace
es devolver TRUE si una cadena contiene SOLAMENTE caracteres validos
(definibles, obviamente).

ver el codigo adjunto (test_string.php3) para ver como funciona.

cualquier bug o duda, me mandan un email!

un abrazo para todos.

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<?php

/* 
Demonstration program of a string checking function, that is:
if string has unwanted characters, it is INVALID. (returns FALSE).
by Arturo Busleiman <buanzox () usa net>.
Thanks go to VULN-DEV () SECURITYFOCUS COM
Hey, my first useful function with PHP :)
*/

$VALID_CHARS_LOW    = "abcdefghijklmnopqrstuvwxyz";
$VALID_CHARS_UP     = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$VALID_CHARS_NUM    = "0123456789";
$VALID_CHARS_SYMBOL = "-_@.";   // you may add whatever you need..
$VALID_CHARS_ALPHA  = $VALID_CHARS_LOW.$VALID_CHARS_UP;
$VALID_CHARS_ALL    = $VALID_CHARS_ALPHA.$VALID_CHARS_NUM.$VALID_CHARS_SYMBOL;

function chequear ($cadena,$validos) {
        for ($z=0;$z<strlen($cadena);$z++)
                for ($i=0;$i<strlen($validos)+1;$i++) {
                        if ($i==strlen($validos)) return(FALSE);
                        if ($validos[$i]==$cadena[$z]) 
                                break; 
                        else 
                                continue;
                }
        return(TRUE);
}

$string1 = "whateveryouwant2check () mpol com ar";
$string2 = "yeah, right!;ls -ald ~user";
$string3 = "378192317";

if (chequear($string1,$VALID_CHARS_ALL)==FALSE) printf("cadena
invalida<BR>"); else printf("cadena VALIDA<BR>");

if (chequear($string2,$VALID_CHARS_ALL)==FALSE) printf("cadena
invalida<BR>"); else printf("cadena VALIDA<BR>");

if (chequear($string3,$VALID_CHARS_ALPHA)==FALSE) printf("cadena
invalida<BR>"); else printf("cadena VALIDA<BR>");


?>