使用ajax显示正在输入的不工作的内容，PHP、ajax和JAVASCRIPT

Using ajax, I'm trying to display what is being typed in the text box, but it's not displaying anything at all for some reason. I know the ajax function itself got called, by using alert inside the function, and I think the real problem is actually in test2.php, but I'm not sure what I did wrong. Please take a look:Using ajax, I'm trying to display what is being