database connection error (1) the mysql adapter ‘mysqli’ is not available.
There are several causes for this error. From CMS updates / upgrades (specifically with Joomla) to your host changing PHP settings or even versions on their side. Luckily there is more than one workaround for this issue:
; Default host for mysql_connect() (doesn't apply in safe mode).
; Default host for mysql_connect() (doesn't apply in safe mode). mysql.default_host = localhost
2. configuration.php (Joomla)
public $dbtype = 'mysqli';
public $dbtype = 'mysql';
3. PHP Settings in cPanel
You can enable the mysqli setting for PHP.
Log in to cPanel, then click on SELECT PHP VERSION.
On the next page, select PHP 5.5 and click ‘Set as current’ . You will see various PHP settings, with mysqli being selected by default for this version.