Prerequisite: The scanning process will consume memory resources. I suggest increasing the memory limit in your PHP.ini to 256M, or more if needed. Install PHPStan composer require --dev phpstan/phpstan Because PHPStan could not read properties in the parent class if the parent is an abstract class, I separated the analysis per folder to explain it easily. 1/ Lib_core (core lib) Download : phpstan_mdl77340_lib.neon and put the file into Moodle's root folder. Run the analysis: php -dmemory_limit=256M vendor/bin/phpstan analyse --configuration phpstan_mdl77341_lib.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. 2/ Lib_dml Download : phpstan_mdl77340_dml.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have the below results: 205    Access to an undefined property core\dml_table_test::$tdb.                             51     Access to an undefined property core\dml_test::$tdb. The $tdb property has been defined in the parent class, database_driver_testcase. 3/ Lib_editor Download : phpstan_mdl77340_editor.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have a bunch of undefined property errors. That was a false alarm because all properties have been defined in the parent class. For example: editor_atto_subplugins_setting::$nosave The $nosave has been defined in the parent class abstract class admin_setting. 4/ Lib_filestorage Download : phpstan_mdl77340_filestorage.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have an empty results. 5/ Lib_form Download : phpstan_mdl77340_form.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have a bunch of undefined property errors. That was a false alarm because all properties have been defined in the parent class. For example: MoodleQuickForm_text::$_flagFrozen The $_flagFrozen has been defined in the parent class HTML_QuickForm_element. 6/ Lib_grade Download : phpstan_mdl77340_grade.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have an empty results. 7/ Lib_classes Download : phpstan_mdl77340_classes.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have a bunch of undefined property errors. That was a false alarm because all properties have been defined in the parent class. For example: core\analytics\time_splitting\single_range::$analysable The $analysable has been defined in the parent abstract class base. 8/ Lib_portfolio Download : phpstan_mdl77340_portfolio.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have a bunch of undefined property errors. That was a false alarm because all properties have been defined in the parent class. For example: portfolio_export_form::$_customdata The $_customdata has been defined in the parent abstract class moodleform 9/ Lib_tests Download : phpstan_mdl77340_tests.neon and put the file into Moodle's root folder. Repeat processes 1 and 2 at the Lib_core but use the above file. Verify that you will have a bunch of undefined property errors. That was a false alarm because all properties have been defined in the parent class. For example: core\core_testable_exporter::$related The $related has been defined in the parent abstract class exporter