A Problem with this Sanitize Message PHP Code?

I have added the below code to my the top of my sendmessage.php file to prevent users in my site to share emails and URLs but this doesn;t work.

What could be wrong with the code? Should I call the functions anywhere ?

function sanitize_message( $message , $email = true, $numbers = true, $url = true )
{
$message = strip_tags( $message );

if($email)
{
//strip email address
$email_regexp = "[_A-Za-z0-9-]+(\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\.[A-Za-z0-9-]+)*(\.[A-Za-z]{2,3})";
$message = ereg_replace($email_regexp, '', $message);
}



//eliminate url from message
if($url)
{
$url_regexp = "(https?://)?(www\.)?([a-zA-z0-9\.])*[a-zA-Z0-9]*\.[a-z]{2,3}";
$message = ereg_replace($url_regexp, '', $message);
}

//eliminate all the bad words
$bad_words = array("skype", ".net", ".com", "org", "biz", "@", "yahoo.com", "gmail", "hotmail", "mail", "e-mail", "msn", "dot",);
$message = str_ireplace($bad_words, '', $message);

return $message; }

Should I call the functions anywhere

Of course you need to call the function for it to be executed.