When I do an INSERT statement that has a SELECT @@IDENTITY at the end, the result is not a resource, but just 1. I suppose that would make sense for an INSERT-only query, but this should be returning a resource for the result. (Transact SQL, the SQL flavor Microsoft SQL Server is powered by, has a special variable @@IDENTITY which returns the last primary key insert).

This alone seems to me to be a bug, but the bigger problem comes next. As sson as I attempt to execute any more queries, either on the same page, or on any others, even if I start a new browser session, PHP chokes. mssql_connect() or _pconnect() returns no error, but any query or mssql_select_db() fails. This continues until I restart Apache.

I've done a trace on the SQL server, and it shows that the last command (the INSERT ... SELECT @@IDENTITY) succeeds, but PHP subsequently stops sending commands. Even when PHP has apparently connected, the Enterprise Manger and trace show no new connections or USE statements.

Here is a test snippet I used:
mssql_pconnect(DB_DSN, DB_USER, DB_PASS);
mssql_select_db('cmxreg');
$ret = mssql_query("INSERT INTO Users (UserName) VALUES ('sql_test') SELECT @@IDENTITY AS UserID");
echo $ret.'<br />';
echo mssql_result($ret, 0, 'UserID');

And the error message for the first run:
Warning: mssql_result(): supplied argument is not a valid MS SQL-result resource in C:\SiteData\htdocs\regadmin\test.php on line 8

And subsequent runs:
Warning: MS SQL: Unable to select database: cmxreg in C:\SiteData\htdocs\regadmin\test.php on line 5
Warning: MS SQL: Query failed in C:\SiteData\htdocs\regadmin\test.php on line 6
Warning: mssql_result(): supplied argument is not a valid MS SQL-result resource in C:\SiteData\htdocs\regadmin\test.php on line 8