Help Creating a Post Category Shortcode

FYI, I’ll be offline for a few days. If you get no response to a new post here, I’m not ignoring you, I’ll answer as soon as I’m able.

No worries. The issue is it does not go in HTML, rather it replaces a line in the shortcode handler, where ever you had placed the current handler, probably functions.php. Here’s the entire handler code with the updated line:

add_shortcode('post_cats', 'sa_show_cats');
function sa_show_cats() {
  $cats = wp_get_post_categories( get_the_ID());
  $html = array();
  foreach ( $cats as $cat ) {
    $url = site_url("/category/{$cat->slug}/");
    $html[] = "<a class=\"sa-cat-links\" href=\"$url\">{$cat->name}</a>";
  }
  return implode( $html, ', ');
}

As PHP code, you do indeed need the $html[] = part 🙂

Then you can style the resulting links with CSS similar to

a.sa-cat-links {
  color: #ffffff;
}

(there was a typo in my previous CSS example, fixed here)

I appreciate your patience while I was away and all through this process.

Oh noes! Did I do that? I think I did 🙁 That’s an extreme, unusual result though. The problem was a repeat of the same earlier error where the function docs were in error about defaults. I copied the code from an earlier post, changed that one line, forgetting about the entire bad documentation issue. I am so sorry, I feel terrible.

The usual result is non-fatal, but code like that is not usually placed in a PHP snippets plugin. Anyway, the corrected line is
$cats = wp_get_post_categories( get_the_ID(),['fields'=>'all',]);

If you are using shortcodes to execute PHP to generate output, you don’t really need a PHP snippets plugin. The shortode declaration code such as what I posted (with correction) can be placed in a theme’s functions.php file. If you have a decent collection of shortcodes, for the sake of organization, you can create your own plugin to contain all of your shortcode declarations. It’s actually fairly easy, making a new .php file with a particular comment at the top and shortcode declarations below. Upload the file to plugins folder. It’ll the show up on the plugins screen where it can be activated.

Here’s the contents of a complete plugin file. You can add other shortcode declarations here as well.

<?php
/*
Plugin Name: sa-custom
Description: Custom code for semperaye's shortcodes 
Author: semperaye
Version: 1.00
License: GPL
*/

add_shortcode('sa_post_cats', 'sa_show_cats');
function sa_show_cats() {
  $cats = wp_get_post_categories( get_the_ID(), ['fields'=>'all',]);
  $html = array();
  foreach ( $cats as $cat ) {
    $url = site_url("/category/{$cat->slug}/");
    $html[] = "<a class=\"sa-cat-links\" href=\"$url\">{$cat->name}</a>";
  }
  return implode( $html, ', ');
}

This does require that you be able to upload a file to your server. Most people use FTP, but your hosting control panel should have a file manager app that will do the job. Placed in a plugin, errors like we experienced will not crash the site, but if it did, you can remove the erroneous plugin yourself through FTP or the file manager.

• This reply was modified 7 years, 9 months ago by bcworkz. Reason: changed shortcode name to sa_post_cats

I just double checked my code from my last post and it worked fine, except for use as a stand alone plugin file, I neglected to include the initial <?php of the file. I’ve since corrected the above code so when you decide to try it as a plugin it’s complete. This would not cause the error you are seeing.

We often see that sort of error because of an issue on the line above the one mentioned. Most frequently, it’s a missing semi-colon ; at the end of the line. Please double check your version against mine above and be sure it matches perfectly, in particular the line with wp_get_post_categories().

I don’t think this next thought applies to you, but on some servers that are running old versions of PHP, the ['fields'=>'all',] syntax is invalid and needs to be changed to array('fields'=>'all',). Since you had your host restore from backup, there’s a remote chance this could be an issue, but the “unexpected ‘$html’ error makes the missing semi-colon or other minor syntax blunder much more likely.

I must say that I’m rather concerned about how my mistake regarding the default arguments for wp_get_post_categories() being in placed within the PHP snippets plugin caused the entire site to crash. When placed as normal code outside of a snippets plugin, nothing awful happens. The code itself doesn’t work but all else does. Some PHP warnings are logged in the error file, and maybe output to the browser, but all else still works. I understand why you like to use such a plugin, and it’s too soon to make major changes now, but some time in the future, you would be well served to learn how to do without snippets by using shortcodes added to the plugin I started.

Sorry to here that. I’m sure this time my code is OK. Tested on my site, but I don’t have a PHP snippets plugin.

It looks like your site is back up, at least the test-post page is working. There’s a mis-match in shortcode names between post content and my code, due to my copying of an old version and updating only part of it in an effort to give you the entire thing in one place. [post_cats] vs. [sa_post_cats] Coordination required, either change the shortcode in post content or the name in the add_shortcode() call.