Help please!

Hello there, I hope I can count on your help. I am migrating a site from MySQL to PostgreSQL. First I just changed the function calls and then I got the error message that PHP was not compiled with PostgreSQL support. Ok, I recompiled as necessary and now the problem is that there was a function being used, called mysql_select_db();, that there is none to use with PostgreSQL instead of it. I really dont know if it is necessary to use the select_db function after the connection to the database. But I think so, because when I try to execute a query without running the select_db function, I am getting the error message: "Fatal error: Call to undefined function: pg_query() in /path/file.php on line 123" Thank's, Wagner