WackoWiki 6.1 uses str_*() functions and as well the match expression not available in PHP 7.4.

• WackoWiki 6.1 Dependencies

Out of the box it is probably better to upgrade the stack or move WackoWiki to an stack with at least PHP 8 0 and MariaDB 10.4 or MySQL 8.0.

Since I no longer have a PHP 7.4 stack for testing, I gave up backporting features to WackoWiki 6.0.

I found a way to raise php to 8. However further found that for 6.1.26 must have MariaDB 10.4. On my hosting I see 10.3 and I can not change it.
Which max version of 6.1 I can install on MariaDB 10.3 ?

MariaDB 10.2 or 10.3 are ok, there is no technical requirement for MariaDB 10.4 except that previous versions are End of support.

Go to constants.php and change DB_MIN_VERSION to

const DB_MIN_VERSION			= ['mariadb' => '10.2.2', 'mysql' => '5.7.7'];		

Now you can install WackoWiki 6.1.26.

Thank you, it worked. The strange limitation that stopped the upgrade scared me. I thought that the wiki requirements were greater than the hoster's capabilities. I don't quite understand the point of chasing the latest PHP and DB.

In this particular case, MariaDB 10.4, it was a feedback from a software packager that many hosters and appliances use for adding WackoWiki. When solving the SQL mode incompatibilities between MySQL 8 and MariaDB I set this threshold for removing NO_AUTO_CREATE_USER for MySQL 8.0 or greater.

Otherwise, MySQL 8 and higher would throw a fatal error when using NO_AUTO_CREATE_USER in SQL session mode.

const SQL_MODE_LAX = [
	'mariadb'	=> 'NO_ENGINE_SUBSTITUTION,NO_AUTO_CREATE_USER',
	'mysql'		=> 'NO_ENGINE_SUBSTITUTION'
];