PHP

update-alternatives java

# Direct
sudo update-alternatives --set php /usr/bin/php7.4
sudo update-alternatives --set php /usr/bin/php8.0
sudo update-alternatives --set php /usr/bin/php8.1

# To ask:
sudo update-alternatives --config php
  
# To show current
sudo update-alternatives --query php

update alternatives java

There are 3 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                      Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-6-openjdk/jre/bin/java   1061      auto mode
  1            /usr/bin/gij-4.4                           1044      manual mode
  2            /usr/lib/jvm/java-6-openjdk/jre/bin/java   1061      manual mode
  3            /usr/lib/jvm/java-6-sun/jre/bin/java       63        manual mode

Press enter to keep the current choice[*], or type selection number: