Why subtract the first 7 characters from token

Question

I am looking to know why we subtract the first 7 token characters during authentication, as in:

substr($_SERVER["HTTP_AUTHORIZATION"],7)

Answer 1

See this example: Best HTTP Authorization header type for JWT

The HTTP header is like that (on one line):

Authorization: Bearer eyJhbGciOiJIUzI1NiIXVCJ9...TJVA95OrM7E20RMHrHDcEfxjoYZgeFONFh7HgQ

So you need to remove the "Bearer " part which is 7 characters long plus one for the space, but since in most languages things are indexed starting at 0, in the above string the token starts at position 7.

See https://jwt.io/introduction/ for more explanations on the header content.