Ttgjyuk

After upgrading my ubuntu from 15.10 to 16.04 LTS, it is showing an error Your PHP installation appears to be missing the MySQL extension when taking any local website from my lamp.

When I tried to reinstall lamp, it shows the following error:

Errors were encountered while processing:
 /var/cache/apt/archives/mysql-server-core-5.7_5.7.12-0ubuntu1_amd64.deb
 /var/cache/apt/archives/mysql-server-5.7_5.7.12-0ubuntu1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

Can any one help?
Thanks in advance.

Just ran into the same error. You'll need to manually enable the mysqli php module and then restart apache:

$ sudo phpenmod mysqli
$ sudo service apache2 restart

After that, it all worked (for me).

Ubuntu 16.04 includes PHP 7.0 that doesn't have old MySQL extension anymore as it has been deprecated for some time and removed in PHP 7.0. You either need to update your application to support MySQLi or pdo_mysql or install PHP 5.6 from PPA (ppa:ondrej/php).

As for the reinstallation problem, I would suggest removing MySQL packages first and then reinstalling them again:

sudo apt-get remove mysql-common
sudo apt-get install mysql-server

When I upgraded my website PHP from version 5.6 to 7.2, I encountered this problem “Your PHP installation appears to be missing the MySQL extension which is required by WordPress”. It turns out that mysql extension is no longer supported in php version 7.2. It is now using mysqli extention. I am using old version of wordpress which still using mysql extension that is why the problem existed. So what I did is upgraded the wordpress to the core. This solve the problem.

Here's the steps I followed when upgrading wordpress manually.
1. First I created a full backup of my website http://fractioncalc.com. This is very important in case of mistake.
2. I download the newest WordPress ZIP file from wordpress.org.
3. I unzipped the file into a local directory of my computer.
4. I went to my website root directory and deleted your ‘wp-includes’ and ‘wp-admin’ directories. I used sFTP connection using Filezilla software.
5. I uploaded the new wp-includes and wp-admin directories from the new version of WordPress I unzipped to my website root directory and replaced the directories I just deleted.
6. I did not delete the wp-content directory or any of the files in that directory. I just copied over the files from the wp-content directory in the new version of WordPress to my existing wp-content directory. All existing files with the same name have been overwritten.
7. I copied all files from the root (‘/’) directory of the new version of WordPress that I unzipped into my website root directory (or the root directory of your WordPress installation). Existing files has been overwritten and new files has been copied across. wp-config.php file was not be affected because WordPress has never distributed with a wp-config.php file.
8. I compare wp-config-sample.php which wass distributed with WordPress but did not find anything to change so I just used the old one.
9. I cleared my browser cache to ensure I can see all changes.
10. I checked the site and there is no error now. Thanks God the upgrade was completed.