Help with AlphaNumeric checker..

[swapshop]

I need help with an alphanumeric checker in php to check all posted variables and generate a link to a page according to its results. any help will be appreciated.

<?php

$redirect = "http://www.mydomain.com/verify.php?verify=1";

function isAlphaNumeric( $str )
   {
       $originalLength = strlen( $str );
       $replacedLength = strlen( preg_replace("#[^A-Za-z0-9_]#", "", $str ) );
       return $originalLength == $replacedlength;
   }

function isEmail( $str )
   {
       $originalLength = strlen( $str );
       $replacedLength = strlen( preg_replace("#[^A-Za-z0-9_@.]#", "", $str ) );
       return $originalLength == $replacedlength;
   }


function isValid( $post )
	{
		if (isAlphaNumeric($_POST[$post]))
	  		{
	    		$redirect .= "&" . $post . "=true"; 
	  		}
		else
			{
				$redirect .="&" . $post . "=false";
			}
	}


isValid ("username");
echo $redirect;


?>

[sneakyimp]

what's the problem exactly?

[swapshop]

i believe the function isValid doesnt work properly. but if i remove the function and place it just as an if statement, it works fine.

[sneakyimp]

you need to indicate that $redirect is a global var within function isValid...like this:

global $redirect;

[laserlight]

You might want to pass $redirect by reference to isValid() instead, e.g.

function isValid(&$redirect, $post)
{
	if (isAlphaNumeric($_POST[$post]))
	{
		$redirect .= "&" . $post . "=true"; 
	}
	else
	{
		$redirect .="&" . $post . "=false";
	}
}

Incidentally, it doesnt make sense to find the length of a string to be tested, then test and replace the unwanted characters with zero length strings, and then compare the length again. It is easier to just test for the unwanted characters, e.g.

function isAlphaNumeric($str)
{
	return !preg_match("#[^A-Za-z0-9_]#", $str);
}

[swapshop]

thanks for the help everyone