What are headers() in PHP?

In PHP header() is used to send a raw HTTP header. It must be called before any actual output is sent, either by normal HTML tags, blank lines in a file, or from PHP

Example :

header(string,replace,http_response_code);

1. string: It is the required parameters. It specifies the header string to send.

2. replace: It is optional. It indicates whether the header should replace previous or add a second header.

3. http_response_code : It is optional. It forces the HTTP response code to the specified value