Are HTTP headers case-sensitive?

Question

In a blog post I use the following PHP to set the content-type of a response:

header(\'content-type: application/json; charset=utf-8\');

I

Answer 1

the Headers word are not case sensitive, but on the right like the Content-Type, is good practice to write it this way, because its case sensitve. like my example below

headers = headers.set('Content-Type'