How-to's Running PHP 8.3 alongside other versions
1. Check the current PHP version
  1. php -v 
PHP 8.3.9 (cli) (built: Jul  5 2024 12:03:23) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.3.9, Copyright (c) Zend Technologies
    with Zend OPcache v8.3.9, Copyright (c), by Zend Technologies
2. List the installed PHP versions and switch to the desired version
  1. sudo update-alternatives --config php 
There are 2 choices for the alternative php (providing /usr/bin/php).

  Selection    Path             Priority   Status
------------------------------------------------------------
* 0            /usr/bin/php8.3   83        auto mode
  1            /usr/bin/php8.2   82        manual mode
  2            /usr/bin/php8.3   83        manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/php8.2 to provide /usr/bin/php (php) in manual mode
3. Verify the current PHP version
  1. php -v 
PHP 8.2.21 (cli) (built: Jul  4 2024 16:26:06) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.2.21, Copyright (c) Zend Technologies
    with Zend OPcache v8.2.21, Copyright (c), by Zend Technologies