Luc Shelton

Enabling Syntax Highlighting in SilverStripe 4

Enabling Syntax Highlighting in SilverStripe 4

Posted 3 years ago Created 3 years ago 3 Minute(s) to read 1 comments

SilverStripe's backend HTML WYSIWYG editor does not come out-of-the-box with support for inserting code snippets or samples with syntax highlighting enabled. Fortunately TinyMCE, the WYSIWYG editor that SilverStripe uses, comes with support for inserting code snippets that make use of PrismJS. In order to activate it as part of your editor, simply go the PHP path under your SilverStripe installation

Open up the configuration file for your SilverStripe installation.

<path to silverstripe>/app/_config.php

Insert the following snippet.


use SilverStripe\Forms\HTMLEditor\TinyMCEConfig;

TinyMCEConfig::get('cms')->addButtonsToLine(2, 'codesample');

You should then find this button as part of your SilverStripe installation's administrative panel editor for all content (see highlighted in red below).



There are a couple of requirements before code samples will appear correctly in your templates or theme.


The TinyMCE codesample plugin makes use of PrismJS for syntax highlighting, and that can be found here.

You will require

  • prism.js
  • prism.css

Once you have downloaded the required files, you can then bootstrap them as part of your template through one of two methods.


Update your root layout template to look something like this in the <head></head>.


<% require themedJavascript('prism/prism.min.js') %>
<% require themedCSS('prismjs/prism.css') %>


Page Controller

Alternatively, if you would prefer to only load these requirements with the page types that will use these asset dependencies, you can also modify the controller for your page type with the code snippet below.



The above snippet should generally be included in the code where the page get's initialized or loaded.

SilverStripe SiteTree

Next, you are going to want to ensure that the PrismJS JavaScript and CSS file are loaded with the PageController on each refresh. Refer to this configuration file snippet below.

Refer to the SilverStripe documentation here about other methods of specifying assets that are required to be loaded by the page.

Known Issues

There is one known issue with the current implementation of the codesample plugin for TinyMCE. SilverStripe seemingly removes the enclosing <code></code> from generated code samples on submission of new content, meaning that code will be improperly highlighted.

There is a slightly hacky work around to this, and it's to simply make use of jQuery to encapsulate all <pre> blocks that specify the "language-*" CSS class.

Refer to the JavaScript below.

            Look at this fucking atrocious hackjob. I had to shim this in because
            tinyMCE likes to strip the <code> tags from my code samples on db insert.

        document.addEventListener("DOMContentLoaded", function(event){
            $('pre').each(function(idx, elem) { $(elem).wrapInner('<code></code>'); });

Simply place this in the <head></head> of your template, and it should fix the problem. This JavaScript code runs once the page's DOM has loaded, and will iterate all <pre> DOM elements in the page that ensure their contents are encapsulated by the <code> tag.

It's currently what I use for fixing the problem with this instance of SilverStripe.



Gravatar for Matt
Posted Feb 11, 2020, 11:06 AM (20 months ago)

Hey Luc,

Thanks for this post! One query - Silverstripe specifies a default set of tags that are allowed in the TinyMCE editor - by default this doesn't include the code tag, which is why it's being stripped out.

You can see the default list of tags in vendor/silverstripe/admin/_config.php, and you can just add your own valid elements by adding to that list. Have you tried this (rather than the jQuery hack you mentioned)?


Gravatar for Luc
Posted Feb 18, 2020, 9:33 AM (20 months ago)

Hey Matt,

Hooray! Someone left a comment on a blog post. :)

Thanks for responding. No, it's unlikely that I have had taken a look at what you've mentioned concerning default tags. I will take a look at that and see if that changes anything.