apache2.service: Control process exited, code=exited status=139 - apache

Question

I install apache2 on ubuntu 18.04. This is fresh install with all default configuration.
I tried to start apache2 but failed. And this is what I see.
# systemctl status apache2.service
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: failed (Result: exit-code) since Wed 2020-03-11 23:17:35 WIB; 13s ago
Process: 9151 ExecStart=/usr/sbin/apachectl start (code=exited, status=139)
Mar 11 23:17:35 xdn.id systemd[1]: Starting The Apache HTTP Server...
Mar 11 23:17:35 xdn.id apachectl[9151]: Segmentation fault
Mar 11 23:17:35 xdn.id apachectl[9151]: Action 'start' failed.
Mar 11 23:17:35 xdn.id apachectl[9151]: The Apache error log may have more information.
Mar 11 23:17:35 xdn.id systemd[1]: apache2.service: Control process exited, code=exited status=139
Mar 11 23:17:35 xdn.id systemd[1]: apache2.service: Failed with result 'exit-code'.
Mar 11 23:17:35 xdn.id systemd[1]: Failed to start The Apache HTTP Server.
When I check /var/log/apache2/error.log, there is empty.
What's wrong with this error?

Answer 1

The "status=139" error must have something to do with having multiple, conflicting versions of PHP enabled.
I am running 18.04 and an old PHP site I run only locally ceased to work. I am guessing aptitude installed and enabled php7.2, possibly when I installed kubuntu-desktop a few weeks back.
Regardless, I had two versions of PHP enabled:
$ cd /etc/apache2/
$ l mods-*/php*
-rw-r--r-- 1 root root 867 Jun 9 2017 mods-available/php5.6.conf
-rw-r--r-- 1 root root 102 Jun 9 2017 mods-available/php5.6.load
-rw-r--r-- 1 root root 867 Mar 2 2017 mods-available/php7.0.conf
-rw-r--r-- 1 root root 102 Oct 1 2018 mods-available/php7.0.load
-rw-r--r-- 1 root root 855 Jul 7 2017 mods-available/php7.1.conf
-rw-r--r-- 1 root root 102 Jul 7 2017 mods-available/php7.1.load
-rw-r--r-- 1 root root 855 Feb 8 2019 mods-available/php7.2.conf
-rw-r--r-- 1 root root 102 Feb 8 2019 mods-available/php7.2.load
lrwxrwxrwx 1 root root 29 Jul 1 2017 mods-enabled/php5.6.conf -> ../mods-available/php5.6.conf
lrwxrwxrwx 1 root root 29 Jul 1 2017 mods-enabled/php5.6.load -> ../mods-available/php5.6.load
lrwxrwxrwx 1 root root 29 May 28 06:05 mods-enabled/php7.2.conf -> ../mods-available/php7.2.conf
lrwxrwxrwx 1 root root 29 May 28 06:05 mods-enabled/php7.2.load -> ../mods-available/php7.2.load
In my case, I am fine with using php5.6, because the site is not online and is purely for my local use only. So disabling 7.2 did the trick:
sudo a2dismod php7.2
Now my php mods-enabled are less confusing to apache3:
$ l mods-*/php*
-rw-r--r-- 1 root root 867 Jun 9 2017 mods-available/php5.6.conf
-rw-r--r-- 1 root root 102 Jun 9 2017 mods-available/php5.6.load
-rw-r--r-- 1 root root 867 Mar 2 2017 mods-available/php7.0.conf
-rw-r--r-- 1 root root 102 Oct 1 2018 mods-available/php7.0.load
-rw-r--r-- 1 root root 855 Jul 7 2017 mods-available/php7.1.conf
-rw-r--r-- 1 root root 102 Jul 7 2017 mods-available/php7.1.load
-rw-r--r-- 1 root root 855 Feb 8 2019 mods-available/php7.2.conf
-rw-r--r-- 1 root root 102 Feb 8 2019 mods-available/php7.2.load
lrwxrwxrwx 1 root root 29 Jul 1 2017 mods-enabled/php5.6.conf -> ../mods-available/php5.6.conf
lrwxrwxrwx 1 root root 29 Jul 1 2017 mods-enabled/php5.6.load -> ../mods-available/php5.6.load
Naturally for a live site one would want to disable php-5.6 and leave the php7.2 enabled, because you should run the newer version in real life.
sudo a2dismod php5.6
sudo a2enmod php7.2
Then the php mods should look like this:
$ l mods-*/php*
-rw-r--r-- 1 root root 867 Jun 9 2017 mods-available/php5.6.conf
-rw-r--r-- 1 root root 102 Jun 9 2017 mods-available/php5.6.load
-rw-r--r-- 1 root root 867 Mar 2 2017 mods-available/php7.0.conf
-rw-r--r-- 1 root root 102 Oct 1 2018 mods-available/php7.0.load
-rw-r--r-- 1 root root 855 Jul 7 2017 mods-available/php7.1.conf
-rw-r--r-- 1 root root 102 Jul 7 2017 mods-available/php7.1.load
-rw-r--r-- 1 root root 855 Feb 8 2019 mods-available/php7.2.conf
-rw-r--r-- 1 root root 102 Feb 8 2019 mods-available/php7.2.load
lrwxrwxrwx 1 root root 29 May 29 17:43 mods-enabled/php7.2.conf -> ../mods-available/php7.2.conf
lrwxrwxrwx 1 root root 29 May 29 17:43 mods-enabled/php7.2.load -> ../mods-available/php7.2.load
Don't forget to resatart the server!
systemctl restart apache2
Thanks to Pavel's comment for inspiring this line of research!

Answer 2

I got this error and I fixed it by enabling PHP version 8.0 (current stable) and disabling PHP version 7.4 (old) in my ubuntu 20.04 by these commands:
sudo a2dismod php7.4
sudo a2enmod php8.0
sudo service apache2 restart
After doing these check your apache status by:
sudo systemctl status apache2.service
It has to be green and must show you active (running).
NOTE: You can do this to any PHP version that you have and want to
change.