Restrict conditions for something with mutliple add_actions?

To put it another way, can I combine the following two actions:
add_action('comment_post', 'fade_comment');
add_action('wp_footer', 'fade_comment');
So that fade_comment is executed in the footer when a comment is posted.

You could tackle this in several ways.

You could register your plugin against the wp_footer action, and then check for some indication that a comment was posted.

Or you could do something a little more bulky, but easier to understand:
register an action against comment_post that sets a global variable (something like global $mybar; $myvar = 1;).
register an action against wp_footer that checks the value of $myvar and executes some action only if $myvar = 1.

Thanks. I’ve tried to get this to work, but although this has removed the errors and doesn’t display the box all the time, it doesn’t seem to work, and nothing happens. I suspect something is wrong with this part of the code, but what?

add_action('comment_post', 'create_myvar');

add_action('wp_footer', 'fade_comment');

function create_myvar() {
global $myvar;
$myvar = 1;
}

function fade_comment() {
if ($myvar == 1) {
echo "<p id='commentsaved' class='fade'>Comment saved!
";
}
}

Inside fade_comment you need to specifically state that you want the global $myvar, otherwise you’re getting a local $myvar for use only inside fade_comment.

function fade_comment() {
global $myvar;
if ($myvar == 1) {
echo "<p id='commentsaved' class='fade'>Comment saved!
";
}
}

You’ll also want to catch (and return) the comment ID in your comment_post action:
function create_myvar($id = '') {
global $myvar;
$myvar = 1;
return $id;
}

If you don’t, plugins that fire after your’s might not get the comment ID, and might break.

Thanks again for the reply, and especially for spotting the bug with the comment id. Still doesn’t seem to be working though.

I’ve put the full source so far here: https://www.cunningtitle.co.uk/fadecomments.txt

Any idea what I’ve done wrong? I’m pretty new to PHP, and had hoped this would be a simple plugin!

What is happening? Anything? Above your add_action() calls, why not stick $myvar = 0; to ensure that there is a global $myvar. I don’t honestly expect that to fix the problem, but it likely won’t hurt.

I’m getting no results at all. It’s acting as though the plugin isn’t even there (and yes, I have made sure it’s activated!)

*desperate bump*
Is this perhaps a WordPress bug then? I don’t think many plugins use comment_post – certainly not to display anything.