Content management software that I use, Joomla! and WordPress in particular, have been complaining for a while now that the PHP version that runs on my servers is outdated and potentially unsecure. Not exactly true, as PHP 5.4 remains part of the official Red Hat/CentOS release, but it would certainly be prudent for me to attempt an upgrade.
I tried to do just that last night, on a test server. And it was a miserable failure, a waste of many hours that I will never get back, to make no mention of the heightened risk of cardiovascular disease due to my elevated blood pressure caused by all that frustration.
The relatively easy part? PHP 7 complaining that its just-in-time compilation feature ran out of memory. Easy-peasy, I can disable JIT. Check.
But then: several of my Joomla! sites refused to run, with a cryptic and ultimately meaningless error message and nothing in the logs. And at least one Joomla! site just got itself into an infinite redirect loop. But why?
I tried many things. I kept looking for answers on Google. Nothing worked. Eventually I took two of my Joomla! sites that are very similar in nature, and began comparing their settings, side-by-side. One worked, the other didn’t. Why?
I then stumbled upon a custom Joomla! module, one that I wrote to support some ads that appear on my sites. This module was installed on the site that failed, but not used on the other. I disabled the module and, presto, the site was working with PHP 7. I re-enabled the module and the site was dead again. So… why?
Well, the module contains some PHP code. Which, after some preamble that allows it to connect to the internal data structures of Joomla!, begins the real work by accessing the MySQL database that contains the actual ads:
$conn = mysql_connect("localhost");
$res = mysql_query("SELECT PAGEID,ADTEXT FROM ...
You see, mysql_ calls have been deprecated and REMOVED from PHP starting with version 7.
And I have hundreds, if not thousands of lines of legacy code* (including, e.g., my calculator museum at rskey.org) that rely on this old library.
So I guess that PHP 7 upgrade will have to wait a while longer. Looks like I have no choice but to rewrite the affected pieces of code everywhere, as there is no other long-term solution. (Even if I find a third-party PHP plugin that re-enables mysql_ codes, how long will that continue to work? How reliable will it be?)
What a muckup. Grumble. And I do have other work to do.