Use Require_once() to include database connection variables correctly

PHP doesn't have function scope like Javascript, so you do not have access to the variables in db_login.php inside the functions of functions.php.

There are multiple ways of dealing with this. Due to your probable use of the server name global constants would probably be a good solution, since nothing can change them.

In your case you can do:

<?php    require_once('db_login.php');      // You have access to $db_server here.      // Create a constant.    define("DB_SERVER", $db_server);    function myfunction() {          // Using a constant. Note that there is no "$".        echo DB_SERVER ;          // Constants are interpreted inside double quotes too        echo "\nMy constant is DB_SERVER";        // ...    }?>

In your case having the server name as a constant is probably appropriate. If you are dealing with something that you want to treat as a true variable, you can pass the variable into the function by value or by reference:

myfunction($variable);  // by valuefunction myfunction($pass_variable_to_me_by_value){    echo $pass_variable_to_me_by_value;    // ...}function myfunction(& $pass_variable_to_me_by_reference){    echo $pass_variable_to_me_by_reference;    // ...}

As a note, in your case, using the global keyword or the $GLOBALS array inside a function is essentially the same as passing by reference., but if you are not passing from the global scope they can be very different (in a Class or from another function for example).

The variables you declare in db_login.php are globals. In order to access them in your function, you need to use the $GLOBALS variable, e.g. $GLOBALS['db_server'], or declare them as global inside your function using the global keyword, e.g. global $db_server.

Inside of the function "myfunction" you don't have access to these variable...

See more in: http://php.net/manual/en/language.variables.scope.php