[code]
<?php
// ==UserScript==
// @name          Select All Checkboxes
// @namespace     http://www.jankoehoorn.nl/
// @description   selects all checkboxes on a page
// @include       http://www.phphulp.nl/profiel/mailbox/*
// ==/UserScript==

(function () {
	var mailbox;

	function check_all () {
		var c = document.getElementsByTagName ('input');
		for (i = 0; i < c.length; i++) {
			if (c[i].type == 'checkbox') {
				c[i].checked = 'checked';
			}
		}
	}
	
	function uncheck_all () {
		var c = document.getElementsByTagName ('input');
		for (i = 0; i < c.length; i++) {
			if (c[i].type == 'checkbox') {
				c[i].checked = '';
			}
		}
	}
	
	function inverse_selection () {
		var c = document.getElementsByTagName ('input');
		for (i = 0; i < c.length; i++) {
			if (c[i].type == 'checkbox') {
				if (c[i].checked == '') {
					c[i].checked = 'checked';	
				}
				else {
					c[i].checked = '';	
				}
			}
		}
	}
	
	var x = document.getElementsByTagName ('form');
	for (i = 0; i < x.length; i++) {
		if (x[i].name == 'mailbox') { // de naam van het formulier op phphulp.nl
			mailbox = x[i];
			break;
		}
	}
	var select_all = document.createElement ('input');
	select_all.type = 'button';
	select_all.value = 'selecteer alles';
	select_all.style.margin = '5px';
	mailbox.appendChild (select_all);
	select_all.addEventListener ("click", check_all, false);

	var deselect_all = document.createElement ('input');
	deselect_all.type = 'button';
	deselect_all.value = 'deselecteer alles';
	deselect_all.style.margin = '5px';
	mailbox.appendChild (deselect_all);
	deselect_all.addEventListener ("click", uncheck_all, false);
	
	var inverse = document.createElement ('input');
	inverse.type = 'button';
	inverse.value = 'keer selectie om';
	inverse.style.margin = '5px';
	mailbox.appendChild (inverse);
	inverse.addEventListener ("click", inverse_selection, false);
})();
?>
[/code]