Guys, where are these classes?

Created a new custom page called header and footer:
In the pages header and footer, these classes are never called. The question is, where are these classes?
They create that is now wasted space on the newly created blank page, listing where you have seen above
March 23rd 20 at 18:55
1 answer
March 23rd 20 at 18:57
1. Function get_header() includes a template header.php.
2. In the template header.php in the body tag is a call to the function body_class().
3. The function body_class() to build attribute class="" for tag body, collecting in a string a specified number of classes, depending on the page/template that is authorized if the user and so that it receives the function get_body_class().
4. Function get_body_class() gets an array of preset dynamic classes depending on the number of conditions, RTL support, on what page (type page) can find what template is used, whether the user is authorized and a number of others.
5. Before returning this array of classes in function is the hook body_class filter, connected to which the list can be changed to fit your needs.

All this is elementary to learn one of the following ways:

1. Turns to look at the documentation of all these functions.
2. Look for these functions in the code WordPress.
3. Start to finally use a decent IDE (PhpStorm for example) and stop lost from 3 pines. Just Ctrl/Cmd + Click on a function and go to it. Then click it and so on. A couple of clicks and everything becomes very clear.
Thank you, very detailed and cool explained! - Thaddeus_Trantow commented on March 23rd 20 at 19:00

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