Create XMLHTTPRequest in IE6 - php

Question

I am applying the following Javascript in a check form function:-
var msg1="";
function check_si_form_info(form,mark,edit){
if(mark==10 || mark=="all"){
if(form.email.value==""){
si_check_email.innerHTML="";
si_check_email.style.height="0px";
form.email.style.backgroundColor="#FFFFFF";
}else{
var i=form.email.value.indexOf("#");
var j=form.email.value.indexOf(".");
if((i<0)||(j<0)){
si_check_email.innerHTML="The email address format is incorrect！";
si_check_email.style.height="auto";
form.email.style.backgroundColor="#FFD5FF";
return false;
}
else{
var email = form.email.value;
xmlhttp=new XMLHttpRequest(); //HERE!!!!
xmlhttp.open('get','si/check_si_email.php?email='+email,true);
xmlhttp.onreadystatechange = function(){
if(xmlhttp.readyState == 4){
if(xmlhttp.status == 200){
msg1 = xmlhttp.responseText;
if(msg1 == '1'){
si_check_email.innerHTML="email address has been used!";
si_check_email.style.height="auto";
form.email.style.backgroundColor="#FFD5FF";
}else if(msg1 == '2'){
si_check_email.innerHTML="";
si_check_email.style.height="0px";
form.email.style.backgroundColor="#FFFFFF";
}else if(msg1 == '3'){
si_check_email.innerHTML="";
si_check_email.style.height="0px";
form.email.style.backgroundColor="#FFFFFF";
}
}//200
}//4
}//onreadystatechange
xmlhttp.send(null);
}
if (msg1 == '1'){
return false;
}
}
}
}
In IE 7 or above, the scripts work perfectly well. But in IE6, the browser always mention the "XMLHttpRequest()" is not defined. If I wish to define it, where and what shall I input?? Thanks a lot!

Answer 1

In IE6 you need to use new ActiveXObject('Microsoft.XMLHTTP') to create the XHR object.
var xmlhttp;
try {
xmlhttp = new XMLHttpRequest(); // real browsers
} catch(e) {
xmlhttp = new ActiveXObject('Microsoft.XMLHTTP'); // <=IE6
}
But you should really use jQuery, it does all the dirty work for you.
Additionally dropping IE6 support wouldn't be a bad thing.

Answer 2

xmlhttp=new XMLHttpRequest();
if(!xmlhttp && typeof ActiveXObject != "undefined"){
try{ xmlhttp=new ActiveXObject("MSXML2.XMLHTTP"); }catch(e){xmlhttp=false;}
if(!xmlhttp)try{ xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); }catch(e){xmlhttp=false;}
}

Answer 3

In the article on AJAX on Wikipedia you have an example how to enable support of AJAX within IE 5, IE 5.5 and IE 6. The example is as follows:
/*
Provide the XMLHttpRequest constructor for Internet Explorer 5.x-6.x:
Other browsers (including Internet Explorer 7.x-9.x) do not redefine
XMLHttpRequest if it already exists.
This example is based on findings at:
http://blogs.msdn.com/xmlteam/archive/2006/10/23/using-the-right-version-of-msxml-in-internet-explorer.aspx
*/
if (typeof XMLHttpRequest == "undefined")
XMLHttpRequest = function () {
try { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); }
catch (e) {}
try { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); }
catch (e) {}
try { return new ActiveXObject("Microsoft.XMLHTTP"); }
catch (e) {}
//Microsoft.XMLHTTP points to Msxml2.XMLHTTP and is redundant
throw new Error("This browser does not support XMLHttpRequest.");
};