How to enable PCNTL on Ubuntu server 16.04

for ubuntu 18 and 20: [replace 7.4.28 with your php version]

1- php -v
result for exapmle: PHP 7.4.28

2- sudo wget https://www.php.net/distributions/php-7.4.28.tar.gz.

3- sudo tar xfz php-7.4.28.tar.gz && sudo rm -rf php-7.4.28.tar.gz

4- cd php-7.4.28/ext/pcntl/

5- sudo phpize
if phpize is not installed you can install it with apt install php7.4-dev

6- sudo ./configure --with-php-config=/usr/bin/php-config

7- sudo make && sudo make install
the result must be like Installing shared extensions: /usr/lib/php/20190902/

8- cd ../../../ && sudo rm -rf php-7.4.28

9- cd /etc/php/7.4

10- sudo sh -c "echo 'extension=pcntl.so' > ./mods-available/pcntl.ini"

11- sudo nano ./cli/php.ini then add extension=pcntl.
repeat this job for sudo nano ./apache2/php.ini or sudo nano ./fpm/php.ini.

12- in all above php.ini there is disable_functions that include pcntl prefix. you must enable which one you want.

13- restart your apache2 or fpm with:
sudo service apache2 restart

14- you can check it with die(extension_loaded('pcntl')); in test.php

note: if you got error : PHP Warning: Module 'pcntl' already loaded in Unknown on line 0, remove extension=pcntl only in cli/php.ini

Source:https://stackoverflow.com/a/64634134/7521380