PHP: Functions have no idea variables even exist

Question

I've noticed an annoying peculiarity in PHP (running 5.2.11). If one page includes another page (and both contain their own variables and functions), both pages are aware of each others' variables. However, their functions seem to be aware of no variables at all (except those declared within the function).

My question: Why does that happen? How do I make it not happen, or what's a better way to go about this?

An example of what I'm describing follows.

Main page:

<?php
$myvar = "myvar.";
include('page2.php');

echo "Main script says: $somevar and $myvar\n";
doStuff();
doMoreStuff();
function doStuff() {
    echo "Main function says: $somevar and $myvar\n";
}
echo "The end.";
?>

page2.php:

<?php
$somevar = "Success!";

echo "Included script says: $somevar and $myvar\n";

function doMoreStuff() {
    echo "Included function says: $somevar and $myvar\n";
}
?>

The output:

Included script says: Success! and myvar.
Main script says: Success! and myvar.
Main function says: and
Included function says: and
The end.

Both pages output the variables just fine. Their functions do not.
WRYYYYYY

Answer 1

You need to use global before using outside-defined variables in a function scope:

function doStuff() {
    global $somevar, $myvar;
    echo "Main function says: $somevar and $myvar\n";
}

More detailed explanation provided at: http://us.php.net/manual/en/language.variables.scope.php

As comments & other answers pointed out accurately, globals can be evil. Check out this article explaining just why: http://my.opera.com/zomg/blog/2007/08/30/globals-are-evil