Often it's required to wrap the value of a MODX tag with some markup, but only if the value is not empty. This single line of PHP will do the trick.
How to make a dynamic list option field for child Resources in the MODX Manager.
A tutorial post on the many options for selectively migrating content or data between MODX sites.
The MODX Resource object has a secret-not-secret field, "properties" in which you can store a JSON object with any kind of data you like. However, there's no UI with which to edit that field. Here's some code to help you utilize it.
MODX CMS comes with powerful member functions that help speed development. Here are five examples.
Advanced tips and tricks to use with getResources, the most powerful Addon component to MODX - or any - CMS.
Do you need a form on your site's front-end where users can upload files? The jQuery Uploadify Plugin makes this simple, and thanks to a user on the Uploadify Forums, extending the capabilities is easy too!
Get attributes from an image file in MODX.
A custom php hook to use with MODX FormIt form processing, to add subscribers to an iContact mailing list.
Teleport is a command line php tool that can help migrate a MODX website in under 15 minutes.