An explanation of the S.O.L.I.D. principles, and how to use them in your PHP scripts.
The decorator pattern explained, with a full and easy to understand example (using PHP).
Adding a background image to a <div> (or any other tag) is easy using CSS. Use these example rules to get a nice gradient that goes over the top of a background image, without adding any additional divs. All in CSS.
A quick into and easy to understand explanation about SQL injection, and what steps you need to do to prevent this affecting your websites.
How to fix (one cause of) "General error: 14 unable to open database file"
The Chain of Responsibility design pattern is gaining in popularity, since being part of the PSR-15 standard (HTTP Request Middleware). Here is a quick overview of it. It let's you chain actions, and often gives them the ability to stop the chain.