HTTP Response code: There are three approaches to accomplish the above requirement, depending on the version.
For PHP versions 4.0: In order to send the HTTP response code, we need to assemble the response code. To achieve this, use header() function. The header() function contains a special use-case which can detect a HTTP response line and replace that with a custom one.
header("HTTP/1.1 200 OK");
For PHP versions 4.3: There are obviously a few problems when using first method. The biggest one is that it is partly parsed by PHP and is poorly documented. Since the version 4.3, the header() function has an additional 3rd argument through which we can set the response code. but to use the first argument should be a non-empty string.
header(':', true, 400); header(‘X_PHP_Response_Code: 400', true, 400);
The second one is recommended. The header field name in this variant is not standardized and can be modified.
For PHP versions 5.4: This versions uses http_response_code() function to makes things easier.
Example: This example uses http_response_code() function to send HTTP response code.
200 HTTP request successfully