Run analysis Install PHPStan composer require --dev phpstan/phpstan Download : phpstan_mdl78159.neon and put the file into Moodle's root folder. Run the analysis: php -dmemory_limit=1G vendor/bin/phpstan analyse --configuration phpstan_mdl78159.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 the below results: 172    Access to an undefined property pdf::$l.                                               201    Access to an undefined property pdf::$CoreFonts.                                     211    Access to an undefined property pdf::$fontlist.                                       378    Access to an undefined property moodle_url::$fragment. PDF: All three properties have been defined in the parent class. Moodle_url: The fragment key will not exist because moodle_url strips the fragment before assigning properties.