In a recent post to his site Tim Cotten talks about how it's possible to screw up singletons in PHP. Singletons are a design pattern that returns the same object once it is created each time the method is called.

“Echo chambers” are an oft-encountered downfall of developers when learning new skills or implementing unfamiliar systems. What begins as a simple question leads to a collection of up-voted knowledge perfectly ready to be copied into your project?—?a great thing for productivity (if you don’t mind getting it wrong).

[...] With that example of echo chambers in mind let’s follow the path of a developer deciding to implement the Singleton pattern in PHP.

He goes through the mindset of a PHP developer wanting to use a singleton in their application, finding an example on the web for their need (making a PDO instance). He gives a sample implementation based on the web examples and tries to execute a test script....with a less than helpful error message. He points out that he's not picking on the source of the example itself, but using it as an example of the "echo chamber" idea perpetuating an example without understanding the logic.

He continues along this same path of thinking with an example from another source - StackOverflow. He cites a specific example, points out the issue and the code it contains. He ends the post with some helpful suggestions on how to "break" this echo chamber and improve the resources in various places on the web.