Undefined Function in JavaScript Plugin

I thought this function was built in to WordPress.

Yes it is. But that looks like some interesting code… As far as I was taught, you’re not supposed to put anything before the /* */ plugin declaration, other than “<?php”. However, the problem may have something to do with this statement in the WordPress codex:

https://codex.www.ads-software.com/Function_Reference/wp_get_current_user

Usage

<?php wp_get_current_user(); ?>

Use the init or any subsequent action to call this function. Calling it outside of an action can lead to troubles. See #14024 for details.

I would contact the plugin developer directly, and ask them what they intended the code to look like because that code doesn’t make any sense. I don’t think you’d want to call wp_get_current_user() without assigning the return value to a variable, like this:

$current_user = wp_get_current_user();

and you would want to call it inside of an action or filter hook.

Well, this is what follows:

wp_get_current_user();
    $user_id = $current_user->ID;
    echo 'User ID: '.$user_id.'<br />';
            $ext_link_param = 'ul='.$user_id;

define( 'EXT_LINK_PARAMS', $ext_link_param );

Should they be in opposite order or something?

I think there’s some code missing. I would contact the developer.

Okay, this is an orphan plugin, due to it being a favor I was given by someone who did not have time to do it. Original plugin:

https://pastebin.com/8Ry0ZFGn

I was told to edit the line:

define( 'EXT_LINK_PARAMS', 'ul=user_id' );

I asked for help on another thread for how to get the user_id for current user and was given:

<?php
    wp_get_current_user();
    $user_id = $current_user->ID;
    echo 'User ID: '.$user_id.'<br />';
            $ext_link_param = 'ul='.$user_id;

define( 'EXT_LINK_PARAMS', $ext_link_param );
?>

That thread is https://www.ads-software.com/support/topic/calling-the-user-id-for-javascript?replies=3#post-2381341. I marked it resolved at the time because I thought it was.

At this time, all I have IS orphan code. I’m trying to attach the current user id to external links, which the plugin does fine if it can call that user id as the param.

OK, try this: Start with a fresh copy of the script you got from the pastebin.com link. Then add the following code right under “function ext_link_params_wp_head() {” and before the “?>”, so you’d have:

function ext_link_params_wp_head() {
$current_user = wp_get_current_user();
$ext_link_param = 'ul='.$current_user->ID;
?>
...

Then change the
<?php echo EXT_LINK_PARAMS ?>
snippet to say
<?php echo $ext_link_param; ?>

Now, change
add_action( 'wp_head', 'ext_link_params_wp', 10 );
to say
add_action( 'wp_print_scripts', 'ext_link_params_wp' );
and just to be on the safe side, change
add_action( 'wp_head', 'ext_link_params_wp_head', 10 );
to
‘add_action( ‘wp_footer’, ‘ext_link_params_wp_head’, 10 );’

For consistency, you can rename the ‘ext_link_params_wp_head’ function to ‘ext_link_params_wp_footer’ if you like, just be sure to change it in both the add_action and the function declaration.

And that should work, although I don’t have a test environment set up right now to test it.

It’s not a pretty solution, but unfortunately the vast number of WordPress plugins aren’t.

Do I need to change this line at all?

define( 'EXT_LINK_PARAMS', 'ul=user_id' );

I did the other changes and it stopped breaking wordpress, but it doesn’t actually add the parameter when I click the links.

My suggestion was to delete that line of code entirely. There’s no reason to define a constant if you’re only going to use the value once, and the constant is computed. That’s just making messy code messier. But you’ll have to change the
<?php echo EXT_LINK_PARAMS ?>
section to say
<?php echo $ext_link_param; ?>

Otherwise, I’m not sure why it’s not working. I usually add echo or var_dump() statements throughout my code when I’m debugging to test if various parts are being executed. For example, right under

function ext_link_params_wp_head() {
$current_user = wp_get_current_user();

I’d probably do something like:
echo 'And the current user ID is: '.$current_user->ID.'!';
If nothing gets printed on the screen, then I know my function isn’t getting called. If “And the current user ID is: !” gets printed to the screen, then I know there’s something up with the wp_current_user() call. Actually, replacing the echo statement with
var_dump($current_user);
would be a better test.

It also helps to use your browser’s built-in script debugging capabilities. If the JavaScript is crashing, you need to know about it, and on what line it’s erroring out on. In FireFox, you can use the wonderful FireBug plugin. In Chrome, you can click the wrench on the top-right, then Tools->Developer Tools. Even IE has pretty good script debugging capabilities, but you’ll have to turn them on in the menu.

In fact, right before the last
});
in your jQuery section, add this:
alert('Hello World!');
and then refresh the page. If you don’t see an alert box pop up with “Hello World”, then either your script isn’t getting called or you have an error somewhere in your JavaScript.

Also try changing
add_action( 'wp_footer', 'ext_link_params_wp_head', 10 );
back to
add_action( 'wp_head', 'ext_link_params_wp_head', 10 );

If you still can’t find the error, paste your entire plugin code here, and I’ll see if I can spot any obvious errors.

On second thought, what you’re trying to accomplish is trivial enough that there’s little point in spending this much time debugging the logic. Probably easier just to write it from scratch:

1) go to your plugins folder and create a new folder called “smpayne2”
2) inside that folder, create a file called “smpayne2.php” and paste the following code into it:

<?php
/*
Plugin Name: smpayne2
Description: Appends current user ID to mailto: anchor tags.
*/
function smp2_enqueue_script() {
	wp_enqueue_script( 'smpayne2', plugin_dir_url( __FILE__ ) . 'smpayne2.js', array( 'jquery' ), '1.0' );
	$current_user = wp_get_current_user();
	wp_localize_script( 'smpayne2', 'smp2Params', array(
		'userID' => $current_user->ID
	) );
} // smp2_enqueue_script
add_action( 'wp_print_scripts', 'smp2_enqueue_script' );
?>

3) in the same folder, create a file called “smpayne2.js” and paste the following code into it:

jQuery(document).ready(function($) {
	$('a[href^="mailto:"]').each(function() {
		var href = $(this).attr('href');
		href += ( -1 < href.indexOf('?') ? '&' : '?' ) + 'ul=' + smp2Params.userID;
		$(this).attr('href', href);
	});
});

4) activate the “smpayne2” plugin in WordPress

This should accomplish what you wanted. There’s less code, and it’s cleaner.