When I installed PHP5.2.8, php_mssql function was not included. php_mssql function is already deprecated or obsolete, but there is a reason why I have to use php_mssql in PHP5.2 series. php_mssql.dll and ntwdblib.dll from php/ext/ directory of xampp1.7.1.
If you drop in PHP alone, php_mssql.dll is not included, but xampp includes php_mssql.dll.