Find the file called: php.ini on your server and follow below steps
With apache2 and php5 installed you need to make three changes in the php.ini file. First open the file for editing, e.g.:
sudo gedit /etc/php5/apache2/php.ini
OR
sudo gedit /etc/php/7.0/apache2/php.ini
Next, search for the post_max_size entry, and enter a larger number than the size of your database (15M in this case), for example:
post_max_size = 25M
Next edit the entry for memory_limit and give it a larger value than the one given to post_max_size.
Then ensure the value of upload_max_filesize is smaller than post_max_size.
The order from biggest to smallest should be:
memory_limit
post_max_size
upload_max_filesize
After saving the file, restart apache (e.g. sudo /etc/init.d/apache2 restart) and you are set.
Don't forget to Restart Apache Services for changes to be applied.
I've just fixed this on my own dev machine. In /etc/phpmyadmin/apache.conf you can see where phpmyadmin is trying to store temp files, e.g.:
php_admin_value upload_tmp_dir /var/lib/phpmyadmin/tmp
Make sure this is writable by the user that apache runs as and has free space.
In my case, on my dev machine, I run apache as my own user rather than the normal www-data or apache user. That tmp dir wasn't writable by my user.
Best Answer
Follow theses steps
Go to the PHP folder -> search for php.ini
Seach for the below line and change it according to your need.
Restart the server to confirm changes.