How do I implement persistent PHP variables?

I am converting some of my php functions to run in MODX. Many work fine. One has a problem I am having trouble solving. The code in question creates <div> blocks with unique ids so they can be hidden and shown by Javascript code.

I have created some simple routines to isolate the area where I need some help. There are two functions, one returns a value, the other bumps it. As included in a standard PHP page all versions work. When called in MODX document via snippets the value is displayed at its highest in all places. I have tried running cached and uncached at all levels. Nothing helps.
------------------------------------------------------------------------
Output from standard PHP page, note the values are different:
Changing a static variable.

STATIC: 22
Bump value.
Value after bump.
STATIC: 33
Bump value.
Value after bump.
STATIC: 44
------------------------------------------------------------------------
Output from MODX, note the values are the same.
Changing a static variable.

STATIC: 44
Bump value.44
Value after bump.
STATIC:44
Bump value.44
Value after bump.
STATIC:44
------------------------------------------------------------------------
I have read much about the order and timing of execution when cached and uncached. Shouldn't this work?
------------------------------------------------------------------------
The php functions, used by both the simple PHP page and MODX.
bump_value and get_value functions at end call one of the three versions, X or Y or Z. All work with the PHP page. None work with MODX.
static.php
<?php
global $g_static;
$g_static = 22;

function bump_valueX() {
global $g_static;
$g_static += 11;
return $g_static;
}

function get_valueX() {
global $g_static;
return $g_static;
}

function bump_valueY() {
$_SESSION["value"] += 33;
return $_SESSION["value"];
}

function get_valueY() {
if ( !isset($_SESSION["value"] )) {
$_SESSION["value"] = 44;
}
return $_SESSION["value"];
}

function bump_valueZ() {
$GLOBALS['static_value'] += 55;
return $GLOBALS['static_value'];
}

function get_valueZ() {
if ( !isset($GLOBALS['static_value'] )) {
$GLOBALS['static_value'] = 66;
}
return $GLOBALS['static_value'];
}

function bump_value() { return bump_valueX(); }
function get_value() { return get_valueX(); }
?>
------------------------------------------------------------------------
The simple html that works:
static_page.php
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>
PHP static test
</title>
</head>
<body>
<?php
session_start();
include "static.php";
?>
<h3>Changing a static variable. </h2>
STATIC: <?php echo get_value(); ?>

Bump value.

<?php bump_value(); ?>
Value after bump.

STATIC: <?php echo get_value(); ?>

Bump value.

<?php bump_value(); ?>
Value after bump.

STATIC: <?php echo get_value(); ?>

</body>
</html>
------------------------------------------------------------------------
MODX resource content version of above:
[[includeStatic]]
Changing a static variable.

STATIC: [[!getStatic]]
Bump value.[[!bumpStatic]]
Value after bump.
STATIC:[[!getStatic]]
Bump value.[[!bumpStatic]]
Value after bump.
STATIC:[[!getStatic]]
------------------------------------------------------------------------
includeStatic snippet:
<?php
include "static.php";
------------------------------------------------------------------------
getStatic snippet:
<?php
echo get_value();
------------------------------------------------------------------------
bumpStatic snippet:
<?php
echo bump_value();
------------------------------------------------------------------------
Can anyone tell me how to make this work or tell me there is a limitation with MODX?

Some of the code seems to have been filtered out by the posting process.
I will try an attachment.