Can't display php syntax errors

[marlin]

I've taken up php programming in my old age with the Abyss web server. I use it for quite few programs that help me keep up with the modern world. But all of a sudden things are falling apart. The fact that I can't get php syntax errors to display isn't helping.

Preliminaries:
Operating system: Linux Mint 22.2 Cinnamon version 6.4.8
Php version: 8.3, FastCGI (Local - Pipes) /usr/bin/php-cgi
MYSQL version: 8.0.43-0ubuntu0.24.04.2

Execution errors, or at least some, display OK; but syntax errors yield a 500 error:

"Looks like there’s a problem with this site
http://localhost:8000/common/test.php might have a temporary problem or it could have moved.
Error code: 500 Internal Server Error
The site could be temporarily unavailable or too busy. Try again in a few moments."

which off course is BS.

I've tried adding to the beginning of each script

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

with no success. I've tried changing the /etc/php/8.3/cgi/php.ini file which I found by displaying the php.ini file itself. The php.ini file itself says there are two versions, development and production. I could only find one ini file; and it says it is the production version. It recommends the following changes, among others, presumably for development:

display_errors = on
display_startup_errors = on
error_reporting = E_ALL

I made the changes, which one can do by opening the file as ROOT. But when I load the ini file by running phpinfo(), I find

display_errors = Off
display_startup_errors = Off
error_reporting = 22527

The 22527 indicates that all errors except for deprecated and strict warnings are reported. I presume that includes syntax error, which is what I want.

I'm guessing that some other php.ini file is being used. But wouldn't know where to look.

Help!

Thank you