Strip All Non Alphanumeric Characters Except Space With PHP

<?php
$string_to_be_stripped = "Hi, I am a string and I need to be stripped...";
$new_string = ereg_replace("[^A-Za-z0-9]", "", $string_to_be_stripped );

function alphanumericAndSpace( $string )
{
return preg_replace('/[^a-zA-Z0-9\s]/', '', $string);
}
echo alphanumericAndSpace( $string_to_be_stripped);
?>