Q:

mysql_select_db() expects parameter 2 to be resource, object given

I'm new in using PHP.  I made something simple to connect to MySQL and select a database:
$conn = mysqli_connect($db_host, $db_admin, $db_pass) or die(mysql_error());
// these variables are previously declared and initialized 

$selected_db = mysql_select_db($db_name, $conn) or die(mysql_error());

When I tested it, I got a successfully-established connection and the following warning:
mysql_select_db() expects parameter 2 to be resource, object given 

Why did this happen?  How can I fix it? 

A:

You are using both mysqli and mysql simply change
mysql_select_db()
With
mysqli_select_db

Reference http://php.net/manual/en/mysqli.select-db.php
updated
When you use mysql_select_db you are supposed to use mysql api and so you have to exatibilish connection to database with mysql sintax mysql_connect Reference
Mysql is now deprecated so it's correct either to use mysqli or PDO 

