Run analysis Install PHPStan composer require --dev phpstan/phpstan Download : phpstan_mdl78160.neon and put the file into Moodle's root folder. Run the analysis: php -dmemory_limit=1G vendor/bin/phpstan analyse --configuration phpstan_mdl78160.neon -vvv | tee result.txt Search for "Access to an undefined property". grep -i "Access to an undefined property" result.txt Verify that you will have a lot of messages like the below: 205    Access to an undefined property core\dml_table_test::$tdb.                             51     Access to an undefined property core\dml_test::$tdb. We can ignore those false alarms from PHPStan because the $tdb property has been defined in the parent class, database_driver_testcase. Other Testing Run mdk phpunit -r -u lib/dml/tests/dml_read_slave_test.php Verify the testing is a successful.