run the following command (requires ag , although advanced grep versions should be able to run it, after all, it's just a regular expression: N.b. If you have ack, you should be able to replace ag with ack in the command below. (sudo apt-get install ack) $ ag '(\$[0-9a-zA-Z_]+|\))(\[['\''"\w$]+\])?{[^\n=}]+}' lib/htmlpurifier --php Verify that you get ZERO matches, that means that there aren't remaining cases. Using moodle-docker (or any >= PHP7.4 RC4 installation) install phpunit (init.php). Verify that there isn't any PHP notice/warning related with lib/htmlpurifier stuff. (Be warned that there may be lots of notices/warnings/errors, here we are only interested in the lib/htmlpurifier ones). Run phpunit (with that PHP7.4 version). Verify that there isn't any PHP notice/warning related with lib/htmlpurifier. (Be warned that there are lots of notices/warning/errors and failures, here we are only interested in the lib/htmlpurifier ones Verify that travis is passing for php71 and php73 (specifically core_htmlpurifier_testcase).