nvm, can be deleted

You can use str_replace (http://www.php.net/manual/en/function.str-replace.php) for simple string replacement.

$new_var = str_replace("@", "(at)", $old_var);

If you're working on text which might contain @ somewhere else, you'll want to look into ereg_replace (http://www.php.net/manual/en/function.ereg-replace.php) to do regular expression replacement.