PHP

Xdebug

Recommended settings for Xdebug 3 and newer

[xdebug]
xdebug.mode=debug
xdebug.start_with_request=yes
xdebug.log_level = 0

This also works for debugging php invoked from the CLI.

Note

Be sure to avoid loading the Zend extensions in the wrong order. See

# THIS IS CORRECT {#this-is-correct}
php -v
PHP 8.0.9 (cli) (built: Jul 29 2021 08:52:24) ( NTS )
Copyright (c) The PHP Group
Zend Engine v4.0.9, Copyright (c) Zend Technologies
    with Zend OPcache v8.0.9, Copyright (c), by Zend Technologies
    with Xdebug v3.0.4, Copyright (c) 2002-2021, by Derick Rethans

Make sure it is NOT:

# THIS IS WRONG {#this-is-wrong}
PHP 8.0.9 (cli) (built: Jul 29 2021 08:52:24) ( NTS )
Copyright (c) The PHP Group
Zend Engine v4.0.9, Copyright (c) Zend Technologies
    with Xdebug v3.0.4, Copyright (c) 2002-2021, by Derick Rethans
    with Zend OPcache v8.0.9, Copyright (c), by Zend Technologies

You can see how things are load and in which order with

php -i # equivalent to <?php phpinfo();.

Compiling PHP beta versions before their release

A quick guide on how to compile PHP to be able to test Matomo with it: