Does case sensitivity in the header affect its processing or comparison?

In the HTTP protocol, headers are case-insensitive, meaning that the case of characters in the header name does not affect its processing or comparison. For example, headers Content-Type, content-type, and CONTENT-TYPE will be interpreted the same.

In PHP, when working with headers (e.g., via getallheaders() or when setting headers), case-insensitivity is usually considered, as it conforms to the HTTP/1.1 standard.

However, header values may be case-sensitive depending on the specific header and its specification.