function ajax(){
	var xhr = null;
	try {
		xhr = new XMLHttpRequest();
		xhr.overrideMimeType('text/xml');}
	catch (e){
		try {
			xhr = new ActiveXObject("Msxml2.XMLHTTP");}
		catch (e){
			try {
				xhr = new ActiveXObject("Microsoft.XMLHTTP");}
			catch (e) {
				xhr = null;}}}
	return xhr;}

function xmlHTTP(xhr, params, pag, funcao1, funcao2, vars){
	if(xhr != null){
		xhr.open("POST", pag, true);
		xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;")	//Deve ser x-www-form p env POST
		xhr.setRequestHeader("Content-length", params.length);						//www.openjs.com/articles/ajax_xmlhttp_using_post.php
		xhr.setRequestHeader("Connection", "close");
		xhr.setRequestHeader("Cache-Control", "no-store, no-cache, must-revalidate");
		xhr.setRequestHeader("Cache-Control", "post-check=0, pre-check=0");
		xhr.setRequestHeader("Pragma", "no-cache")
		xhr.send(params);
		xhr.onreadystatechange	= function(){
			if(xhr.readyState	== 4){
				if(xhr.status	== 200){
					eval(funcao1 + '(xhr.responseXML, vars);');}
				else {
				// parte q mostra o erro
				}}
			else{
				
				}}}}