Cleaning up/Formatting user input

We use below function to clean up a user input:

function x_site_safe($input,$do_quot=true,$remv_quot=false) {
   $input = preg_replace("/</","",$input);
   $input = preg_replace("/>/","",$input);
   $input = preg_replace("/\(/","",$input);
   $input = preg_replace("/\)/","",$input);
   if ($do_quot)   $input = preg_replace("/\"/","&quot;",$input);
   if ($remv_quot) $input = preg_replace("/\"/","",$input);
   return $input;
}

Usage:
x_site_safe($input) : remove >, <, ( , ), and change " to &quot
x_site_safe($input, false): remove >, <, ( , and )

For example: (combine with stripslashes and trim)

$str = (isset($_GET['v'])) ? stripslashes(trim(x_site_safe($_GET['v'],false))) : "";