How do I embed PHP code in JavaScript?

If your whole JavaScript code gets processed by PHP, then you can do it just like that.

If you have individual .js files, and you don't want PHP to process them (for example, for caching reasons), then you can just pass variables around in JavaScript.

For example, in your index.php (or wherever you specify your layout), you'd do something like this:

<script type="text/javascript">
    var my_var = <?php echo json_encode($my_var); ?>;
</script>

You could then use my_var in your JavaScript files.

This method also lets you pass other than just simple integer values, as json_encode() also deals with arrays, strings, etc. correctly, serialising them into a format that JavaScript can use.

If you don't want to use javascript, you can handle it via php. Take a look at this lib: http://code.google.com/p/php-mobile-detect/. And then you could do something like:

<?php
include 'Mobile_Detect.php';
$detect = new Mobile_Detect();

if ($detect->isMobile()) {
    header('Location: yourpage.php');
    exit(0);
}

erk. The correct answer would be ajax call backs. You can either manually code the js to hook into the wicket js, or you can setup the callbacks from wicket components in java. For example, from AjaxLazyLoadPanel:

        component.add( new AbstractDefaultAjaxBehavior() {

        @Override
        protected void respond(AjaxRequestTarget target) {
            // your code here
        }

        @Override
        public void renderHead(IHeaderResponse response) {
            super.renderHead( response );
            response.renderOnDomReadyJavascript( getCallbackScript().toString() );
        }

        }

This example shows how to add call back code to any Component in Wicket. After the OnDomReady event fires in your browser, when loading a page, Wicket will cause it's js enging, to call back into your code, using Ajax, to the 'respond' method shown above, at which point you can execute Java code on the server, and potentially add components to the ajax target to be re-rendered.

To do it manually, from js, you can hook into wicket's system by printing out getCallbackScript().toString() to a attribute on a wicket component, which you'll then be able to access from js. Calling this url from js manually with wicket's wicketAjaxGet from wicket-ajax.js.

Check out the mailing list for lot's of conversation on this topic: http://www.nabble.com/Wicket-and-javascript-ts24336438.html#a24336438