PHP To Leave Only Letters And Numbers

When passing variables in URL's it's smart to validate that the variables are what you expect them to be.

An easy way to do this is to always name your variables passed via url with the rule: they can only be alphanumeric, or only contain numbers and letters. It's hard for people with bad intentions to affect your site with the only option of using alphanumeric characters.

There are many other reasons to want to validate some input is only letters and numbers. Here is some basic code to do it:

<?php
$originaltext = "This isn't a very cle!!@n stre$$*ing.";
$alphanumerictext = ereg_replace("[^A-Za-z0-9]", "", $originaltext );
echo $alphanumerictext;
?>

The code will return "Thisisntaveryclenstreing"