Tiny AJAX

This is a very tiny javascript code to do an AJAX Request:

/*
 m: method ("get", "post")
 u: url
 a: async (true) or sync (false)
 c: callback (with 'xhr' as a parameter)
 d: post_data (the data to post)
*/
function tiny_ajax(m,u,a,c,d){with(new(this.XMLHttpRequest||ActiveXObject)("Microsoft.XMLHTTP"))onreadystatechange=function(){readyState^4||c(this)},open(m,u,a),send(d)}

And an example:

tiny_ajax('get', 'http://www.google.com', true, function(xhr) {
    alert(xhr.responseText)
})