It’s possible that when you installed phpMyAdmin, the version in the repository (phpMyAdmin v4.6.6) was not fully compatible with PHP 7.2. There is a newer version available on the official website (v4.8 as of writing), which fixes these compatibility issues with PHP 7.2.

This error is caused by a line of code in /usr/share/phpmyadmin/libraries/sql.lib.php.

If you don’t want to wait for the repositories to update with the latest version, you can manually upgrade to the latest version of phpMyAdmin yourself.

Alternatively, you can make a small change to sql.lib.php to fix the error.

Firstly, backup sql.lib.php before editing.

sudo cp /usr/share/phpmyadmin/libraries/sql.lib.php /usr/share/phpmyadmin/libraries/sql.lib.php.bak

Edit sql.lib.php in nano.

sudo nano /usr/share/phpmyadmin/libraries/sql.lib.php

Press CTRL + W and search for (count($analyzed_sql_results['select_expr'] == 1)

Replace it with ((count($analyzed_sql_results['select_expr']) == 1)

Save file and exit. (Press CTRL + X, press Y and then press ENTER)

Note that this is just a temporary fix and other compatibility issues may crop up until you update phpMyAdmin to the latest version.