Not all of PHP installation has short tags support. There are a few installations that have turned it off. If the short tags are turned off, only <?php and <script> tags are recognized. The <? tags are not allowed and the scripts are broken.
If you want to use the PHP short tag <? you need [...]

Ajax stands for Asynchronous JavaScript and XML. AJAX is not a new programming language, but a new technique for creating better, faster, and more interactive web applications.
With AJAX, a JavaScript can communicate directly with the server, with the XMLHttpRequest object. With this object, a JavaScript can trade data with a web server, without reloading the [...]