PHP 5 - Variable scope across include files with no classes or functions

Question

I've read through many, many threads on this and still can't wrap my head around it.

Here's my basic issue:

header.php includes a file called navigation.php. Within navigation.php, $previous and $next are defined. Using echo statements I have verified they have values.

Next, header.php includes a file called backnext.php. I need backnext.php to know the values of $previous and $next. If I declare them as global at the top of backnext.php, I don't get errors, but echo statements show they are empty. If I don't, I get an undefined variable error.

Where exactly do I need to declare them as global to have backnext.php be able to read their values correctly?

None of these files are using functions or classes.

Answer 1

If none of these files have functions or classes then $prev and $next are in the global scope and should be seen by all your include files and you shouldn't need to use the global keyword.

It sounds like the order of your includes may be a bit wrong.

Update:

If I understand correctly you have something like this:

header.php:

<?php
echo "In header.php\n";

require_once("navigation.php");
require_once("backnext.php");

echo "Also seen in header.php:\n";
echo "prev=$prev\n";
echo "next=$next\n";
?>

navigation.php:

<?php
echo "In navigation.php\n";
$prev = "Hello World#1";
$next = "Hello World#2";
echo "Exiting navigation.php\n";
?>

backnext.php:

<?php
echo "In backnext.php\n";
echo "prev=$prev\n";
echo "next=$next\n";
echo "Exiting backnext.php\n";
?>

If I run this I get:

In header.php
In navigation.php
Exiting navigation.php
In backnext.php
prev=Hello World#1
next=Hello World#2
Exiting backnext.php
Also seen in header.ph
prev=Hello World#1
next=Hello World#2

backnext.php is able to see both $prev and $next.