Regarding connecting to a MySQL db...

my back end admin control panel for my website has a dynamic content setup with a navigation menu that allows the admin to access different information about clients and orders. each page that the admin selects has specific queries.

my question: how often do I have to connect to the database? do I need to make a connection on each page? or can I connect once (on the main admin page). and that connection still be active for each page? or do I have to connect on each page that is accessed?

I could do some trial and error coding, but with the number of pages involved, I thought it may be faster to ask here

Thanks in advance!

Basically you need to connect to db every time you use queries, but yet again it depends on your page structure.

Consider adding db connection in a separate file and then just include that file on every page.

miki86 is right. You need to connect to database on each page. Database connection is closed at the end of each page and you have to create it again on next page.

I think it simplifies things to think of it in terms of requests, 'page' is a little ambiguous.

For every request, you need call mysql_connect prior to executing any queries. If you're still having trouble understanding, try explicitly passing the connection resource to each mysql_* function call (doing this is normally optional).

PHP Code:

$conn = mysql_connect('localhost', 'user', 'pass');
/* ... */
$res = mysql_query($query, $conn); 


This way you'll know you have to set $conn before running any queries. Just make sure $conn is global in scope otherwise you won't be able to access it in function or method calls.

Also, note that variables are persistent across includes. For example, the following should work fine:

PHP Code:

//main.php
$conn = mysql_connect('localhost', 'user', 'pass');

require_once('foo.php'); 


PHP Code:

//foo.php

mysql_query($query, $conn);