pagination using $_GET or $_POST

I’ve poured over the forums and codex to get this working for days. Some of my posts have a lot of image content that slows siteload down considerable as one page. <!–nextpage–> does not work to my satisfaction, so I need to customize a script. I tried using $_GET, but with pretty permalinks, it’s not working right (whether in preview or post mode), and the info here is not sufficient for a solution.

So I’m down to using &_POST with PHP_SELF as form action. While my numbers show on my development .php page, it won’t show in a post. this is my code:

<form action="[php] htmlentities($_SERVER['PHP_SELF']); [/php]" method="POST">
[php]

$said_page = 1;
$last_said_page = 10;
$last_said_page++;
do {
    echo "<input type='submit' name='$said_page' value='$said_page' />  ";
} while ($said_page++ !== $last_said_page);

[/php]
</form>

What am I doing wrong here?