Can't wrap my head around Global arrays - php

Question

I asked about this last night but the answers told me to research global arrays. After spending an entire day trying to solve this I have sacrificed my man card and I'm now seeking help. I have 3 files that work together to echo a variable $body. The 3 files are login.php, global.php, and theme.php.
The login file works as expected and displays a message that I'm already logged in when I replace $body with echo, but to incorporate my theme easily and effectively I want to use the variable $body for placement reasons. When I echo $body in the theme file nothing appears. heres a quick example of my files
Login.php
<?php
include('../tools/global.php');
$body="
some scripting here";
?>
global.php
<?php
function function1(){
global $body;
}
function1();
print_r($body);
include('../theme/default.php');
include('config.php');
?>
default.php aka theme.php file
<table border='0'>
<tr>
<td colspan='2'>
<center>bar</center>
</td>
</tr>
<tr>
<td width='10%'>
hey<br>hey<br>
</td>
<td>
hello
<?php
echo $body;
?>
</td>
</tr>
</table>
Okay so how exactly would I register the global $body so it will always echo $body in the theme file? I have tried many of different things but nothing seems to work.

Answer 1

Login.php includes global.php but $body is defined in Login.php only AFTER global.php was included - that's why you can't use it in global.php
If you want to use it in global.php - declare it there!

Answer 2

I think the advice you were given about looking into globals was probably bad advice. Globals are almost never the answer. You are also using them incorrectly. The global keyword allows you to use a global variable (defined outside a function) within a function. It's that simple. It's much better practice, though, to pass the variable into the function as an argument. When you have stuff that you want to use repeatedly throughout different files, put it in a function in an include file, instead of just the body of the include file. For instance, in global.php, you have:
<?php
function renderPage($body) {
?>
<table border='0'>
<tr>
<td colspan='2'>
<center>bar</center>
</td>
</tr>
<tr>
<td width='10%'>
hey<br>hey<br>
</td>
<td>
hello
<?php
echo $body;
?>
</td>
</tr>
</table>
<?php
}
?>
Then in login.php:
<?php
require('global.php');
$body = 'This is the login page.';
renderPage($body);
?>