How to avoid including database connection file in every page?

Question

Suppose i have a page config.php which contains

<?php
$username = "your_name";
$password = "your_password";
$hostname = "localhost"; 

//connection to the database
$dbhandle = mysql_connect($hostname, $username, $password)
  or die("Unable to connect to MySQL");
echo "Connected to MySQL<br>";
?>

I know i need to include this config.php file where i want to ensure database connection.But is there any way to do this globally so that i don't need to include connection file in every required page ?I am asking so because i have seen lots of script where they are running query in a particular php page without including the database connection file!

Answer 1

My usual approach is to create an autoloader function to pull in classes as I need them and have a class handle the DB connection. However that might be a bit excessive for some projects. Also that config still needs to be included prior to my code that calls for a class and expects something to go and get it.

A lot of open source PHP software will set values like this in a config file which gets included very early on along with any libraries etc.

For Example (LM)NucleusCMS uses the config file to load the global functions and other core classes and that way the only thing a PHP script needs to do is ensure that config.php has been included.

Sometimes code you are looking at is intended to be included at run time by other code and so trusts that these settings are already in place. For example I am currently working on a project that redirects all calls to PHP files to start.php which does what is needed and then calls for the file after that and then finally calls for the template to process the output.

If you really want to do no includes at all then there is one other option but it is not recommended. You could set the php.ini directive auto_prepend_file and have the file included in EVERY script the server runs. As I said, you probably do not want this.

However that said if you would like to have the script handle the including for you and this is important then using the .htaccess and start.php example (actually ./engine/start.php) then this might work for you better than fooling about with ini directives. However the downside is that you need to check that your .htaccess redirects are working properly passing the filename back to the start.php and then make sure that some naughty user is not asking your script to do something bad. Once you have sanitised and sanity checked the input then you can go ahead and require_once($filename)...

My .htaccess looks a bit like this:

RewriteEngine on
RewriteRule ^(.*).php?$ ./path/to/start.php?page=$1 [QSA,L]

However, as I have said unless you have a specific need to do this then it would be safer not to as you are allowing ANY input into the include/require line and have to spend a lot of resources on EVERY page load making sure the request is safe.

To be honest the most common best practice is to have a file called, say common.php, and have all of the includes that the scripts need to get to in there and just

require_once('./path/to/common.php'); 

at the top of every page. If your project ends up with a lot of classes and/or libraries in it then you might be glad that you did.