Nice question, I don't know but you could use PDO::quote() with the PDO_DBLIB driver.
EDIT: Seems like this guy got it from StackOverflow:
function mssql_escape($data) {
if(is_numeric($data))
return $data;
$unpacked = unpack('H*hex', $data);
return '0x' . $unpacked['hex'];
}
Another option:
function mssql_escape($str)
{
if(get_magic_quotes_gpc())
{
$str= stripslashes($str);
}
return str_replace("'", "''", $str);
}