Unable to install WordPress due to a mysqli error

Symptoms

Automatic WordPress installation fails in ispmanager 6:

• When selecting PHP CGI mode, the error «System requirements are not met: php-extension: json, mysqli» is displayed;
• When selecting Apache as PHP mode, the error «Failed to install the application 'WordPress'» is displayed;

The error is registered in the control panel log at /usr/local/mgr5/var/ispmgr.log

Sep 25 15:22:55 [2999879:101550] aps ERROR Failed to install aps: 'PHP Fatal error:  Uncaught Error: Call to undefined function PHPMailer\PHPMailer\mail() in /var/www/user2112/data/www/isptest.test/wp-includes/PHPMailer/PHPMailer.php:880

Causes

The mail() function is disabled in PHP (CGI) settings.

Solution

Enable the mail() function in the PHP settings used for your WordPress site.

To do this, go to the PHP section, select the desired PHP version and click Advanced PHP settings. Find the disable_functions parameter and delete the «mail» value from the settings. Save the changes.