Nice job and well written. A nice addition would be how to use pdo. I'm appalled by the number of ressources I see online which are using the old mysql api.
Recently authored articles? We have an internet filled with 20 years of PHP tutorials, and unfortunately for beginners there's not an easy way to evaluate if something utilizes modern best practices or is an Experts Exchange post from 2001.
Anyway, Google links are pretty much already ordered by popularity.
A nice big "this answer is outdated, see [other answer]" note does wonders.
This is particularly distressing in the case of security vulnerabilities. Vulnerable code being copied from Stack Overflow into consumer applications isn't hypothetical, it's been empirically demonstrated (https://www.aisec.fraunhofer.de/en/stackoverflow.html), yet the community and company refuse to accept responsibility and address the problem. (Of course the developer creating the application is more responsible, but Stack Overflow is in a position where they could help protect innocent end users and the common good.)
Pinning of accepted answers to the top of the list was a good idea when the site was young. These days, it prevents updated better answers from taking the place of ten-year-old misinformation.
For what it's worth though, my understanding is mysql_ functions are removed completely as of PHP 7. So that old documentation will just not work, rather than teaching people the least secure option of how to write their website.
mysql_query($sql, $link);
mysqli_query($link, $sql);
Then I realized it was pretty amazing that it lasted that long in the first place.
this call came in late 2017 saying "hey, we migrated the site and it doesn't work". There was some change in PHP5.6 and the initial PHP4 code had some "by reference" class stuff that wasn't working any more. It was a small change to get it working again, but there was enough PHP4 in it that a move to PHP7 wasn't going to work without a lot of work. I'd suggested a rebuild, which... wasn't too well received. Pointing out that they'd had 16 years of functionality on a web codebase (with no other costs) was probably as much ROI/value as you'd ever be able to get out of anything.