Best way to pass data from PHP to JavaScript for my particular case

Question

I've built an online community in Drupal with a homepage that is kind of like the Facebook wall. You see the 25 most recent posts, with the two most recent comments below those posts. There is also a textarea right below those comments so that you can quickly post a new comment on a particular post.

These Facebook-style posts have a lot of functionality built into them via JavaScript. Clicking a "view all comments" link directly below a post makes an AJAX call that grabs all the comments for that post and displays them right below it. You can also mark posts as helpful, as the solution to your question, edit comments inline, etc. All of these actions require AJAX requests, which means that the JavaScript making the request needs to know essential information such as the Node ID (the unique identifier of the post), the comment ID (unique identifier of the comment), etc.

My initial implementation had these pieces of essential data sprinkled all over the posts, making it more complicated to write the JS that needed to find it. So my second implementation simply output all this data into a JSON-compatible string in the main wrapping element of each post. While this made it much easier for the JS to find the data it needed, writing JSON as a string is a pain (escaping quotes, no line breaks).

So now I have a third idea, and I'm looking for feedback on it prior to implementation. The idea is to create a single global JS Array for all these posts that contains within it objects that hold the data for each post. Each element in that array would hold the necessary data needed for the AJAX calls. So it would look something like this:

Facebook-style post template

<div class="post" data-postindex="<?php echo $post->index; ?>">
    <!-- lots of other HTML for the post -->
</div>
<script type="text/javascript">
    globalPostArray.push({
        nid: <?php echo $post->nid; ?>,
        authorID: <?php $post->authorID; ?>,
        //etc. etc. etc.
    });
</script>

The result of the above code is that when a link gets clicked that requires an AJAX request, the JS would simply traverse the DOM upwards from that link until it finds the main .post element. It would then grab the value of data-postindex in order to know which element in globalPostArray holds the data it needs.

Thoughts? I feel like there must be some standard, accepted way of accomplishing something like this.

Answer 1

I've never heard of a standard way to "pass" information between PHP and Javascript, as they are a server-side and client-side language, respectively. I would personally use a hybrid of your second and third solutions.

Store the post id in a data-postindex attribute (data attributes are newish, and the "right" way to store small amounts of data). But I would still just use a JSON array for the rest, as storing lots of data in data-attributes (and escaping them!) is potentially problematic. PHP has a json_encode function that takes care of all the escaping and such for you - just build a PHP array (say, $postdata) like you normally would, and then throw this in your post template:

<script type="text/javascript">
    globalPostArray.push(<?php echo json_encode($postdata) ?>);
</script>

Where $postdata is something like the following:

$postdata = array(
    'nid' => 5,
    'authorId' => 45
    ...etc...
);

It should be easy enough to generate such an array from your existing code.

I wrote a blog post a while back about my implementation of this kind of thing, but it sounds like all you need is a pointer at json_encode.