Question

I have 2 includes on a page. Let’s say they’re the header and footer:

<?php
include('header.php');
include('footer.php');

I need to use a variable from the footer in the header. Is this possible?

Answer 1

Unless there’s a reason you can’t, the simple solution is to set the variable used in inc2 in inc1 instead.

When a script is included outside of any function, the script executes in global scope, so anything it sets or defines that is scoped will have global scope. If a script is included within a local scope (such as in a function), the script executes in the same scope, so anything it defines is local. Note the included script can access variables local to a function.

function foo($x) {
    $bar = 'bam';
    include 'script.php'; # script.php can access $x and $bar
}

However, global variables can be problematic. A better approach is to break down tasks into separate modules. Most modules are library scripts: they only define things (functions, classes) and don’t execute anything directly. The entry point (the top level script) doesn’t define anything; instead, it serves to connect everything and as a starting-off point for computation. Here’s a simple example with a database connection:

<?php
include_once('DB.php');
include_once('header.php');
include_once('footer.php');

$db = DB::connect();
header($db);
footer($db);

While technically $db is a global variable (note that this is merely sample code, rather than production code), it’s not to be accessed anywhere outside this script. Instead, it’s passed around according to the rules of capabilities (which was designed for security purposes, but the rules are actually just good OOP principles).