Psalm Requires PHP >= 7.1 and Composer.
composer require --dev vimeo/psalm
./vendor/bin/psalm --init [source_directory=src] [config_level=3]
config_level represents how strict you want Psalm to be.
1 is the strictest,
8 is the most lenient.
$ ./vendor/bin/psalm --init src 3 Config file created successfully. Please re-run psalm.
Then run Psalm:
Psalm will probably find a number of issues - find out how to deal with them in Dealing with code issues.