Best video resources to learn PHP SPECIFIC for wordpress

What are some of the best video resources to learn PHP SPECIFIC for wordpress?

I’m aware of w3 schools and plan to use them, however I want to know how wordpress works with PHP and coding, how all the php files and structures, files, folders are linked inside WordPress.

I want to teach myself PHP, CSS, HTML, but I want to know how to apply this knowledge to wordpress speficially.

Best resources (video preferably) and … GO!
Many thanks guys.