Connect a different database on the log-in process only - php

Question

The codes I'm working on are a bit confusing since I didn't make this one. But what I want to do is get the login information from a different database. I can't just modify the config.php of the database connection cause it will mess up the whole system.
I tried the trick to connect 2 databases by storing different variables on mysql_connect. But in this case, its a bit confusing.
Is there another way to just change the database connection only once in the logging in process?
login.php (the php file once the login info is submitted)
include("inc/config.php");
$connection = mysql_connect($hostname, $user, $pass) or die ("Unable to connect!");
$query = "SELECT * FROM clients WHERE name = '$name' AND password = '$password'";
$result = mysql_db_query($database, $query, $connection);
$date_in = date("Y-m-d");
$time_in = date("H:i:s");
$client_accesslogin = $name;
if (mysql_num_rows($result) == 1)
{
session_start();
session_register('time_in');
session_register('date_in');
session_register('client_accesslogin');
session_register('remoteaddr');
$_SESSION['time_in']=$time_in;
$_SESSION['date_in']=$date_in;
$remoteaddr = $_SERVER['REMOTE_ADDR'];
$ipaddr = $_SERVER['REMOTE_ADDR'];
$client_accesslogin = $_SESSION['client_accesslogin'];
session_register("client_id");
session_register("client_name");
session_register("client_email");
session_register("client_company");
list($clientid, $name,$first_name,$last_name, $pass, $email, $company) = mysql_fetch_row($result);
$client_id = $clientid;
$client_name = $name;
$fname=$first_name;
$lname=$last_name;
$client_email = $email;
$client_company = $company;
$cisloggedin = 'Yes';
session_register("cisloggedin");
session_register("fname");
session_register("lname");
header("Location: menu.php");
mysql_free_result ($result);
mysql_close($connection);
}
$connection = mysql_connect($hostname, $user, $pass) or die ("Unable to connect!");
$query = "SELECT * FROM admins WHERE name = '$name' AND password = '$password'";
$result = mysql_db_query($database, $query, $connection);
$date_in = date("Y-m-d");
$time_in = date("H:i:s");
$accesslogin = $name;
if (mysql_num_rows($result) == 1)
{
session_start();
session_register('time_in');
session_register('date_in');
session_register('accesslogin');
session_register('remoteaddr');
$_SESSION['time_in']=$time_in;
$_SESSION['date_in']=$date_in;
$remoteaddr = $_SERVER['REMOTE_ADDR'];
$ipaddr = $_SERVER['REMOTE_ADDR'];
$accesslogin = $_SESSION['accesslogin'];
session_register("client_id");
session_register("client_name");
session_register("client_email");
list($clientid, $name, $pass, $email) = mysql_fetch_row($result);
$client_id = $clientid;
$client_name = $name;
$client_name = "admin";
$client_email = $email;
$isloggedin = 'Yes';
session_register("isloggedin");
header("Location: menu.php");
mysql_free_result ($result);
mysql_close($connection);
}
else
{
mysql_free_result ($result);
mysql_close($connection);
header("Location: index.php");
exit;
}
?>
That works. But If I remove the included config.php and just add the connection:
$database = "invoices";
$user = "root";
$pass = "";
$hostname = "localhost";
It doesn't login. I don't get it. the inc/config.php has some codes with the connection but why can't i just add the connection itself without using include?

Answer 1

I'm doing to assume that there's a dedicated page for login processing?
In which case you can just make a new config.php and connect to that db only on the login page?
A bit of your code or structure would help.

Answer 2

mysql_select_db() function sets the active MySQL database.
Syntax
bool mysql_select_db ( string database_name [, resource link_identifier])
mysql_select_db() attempts to select existing database on the server associated with the specified link identifier.
Returns TRUE on success, or FALSE on failure.
We can select database in mysql server by using mysql_select_db function. mysql_select_db() selects the current active database on the server that is associated with the specified link identifier. If no link identifier is specified, the last opened link is assumed. If no link is open, the function will try to set a link as if mysql_connect() was called without arguments.

Answer 3

Made a function to connect to your database, also to close your connection.
function connect(user, pass, location)
function disconnect()
then you connect to your first db, do your operations. Close it and then open a new connection to the other db and do also your operations.
If you want to maintain 2 connections at the time, you could save your instances to variables
and do:
mysqli_select_db($instance1, 'SELECT ...');
mysqli_select_db($instance2, 'SELECT ...');
Also escape your variables in your query :)