The Shortest PHP Code for Returning HTTP Response Code

The Documented Code

In PHP documentation, the suggested code for returning 404 Not Found is:

header("HTTP/1.0 404 Not Found");

I wanted the shortest possible code for the PHP framework I'm writing. So, I don't want an array of response texts that accompany the codes; that is simply way too long.

Testing the Alternatives

I decided to test a bunch of variations to see if I could make it shorter. These are what I tested and the results:

header("HTTP/1.1 404");   //works
header("HTTP/1 404");     //works
header("HTTP/ 404");      //works
header("HTTP 404");       //doesn't work, returns 200 OK
header("HTTP/1.1",0,404); //doesn't work, returns 200 OK
header("HTTP/1",0,404);   //doesn't work, returns 200 OK
header("HTTP/",0,404);    //doesn't work, returns 200 OK
header("HTTP",0,404);     //works
header("",0,404);         //doesn't work, returns 200 OK
header("/",0,404);        //works
header("1",0,404);        //works
header(1,0,404);          //works
header(0,0,404);          //works

Found it!

The Shortest Code

So, the shortest code is:

header(0,0,404);

It is a surprise for me because the documentation says that the 1^st parameter must not be empty for the 3^rd parameter to work, and integer 0 is considered empty by the function empty().

I tested this in PHP 5.3.10. Of course, you could use http_response_code() in PHP 5.4.0 and up, but it's not as short.

I didn't test all possible response codes, but the ones I did test (400-420 and 500-510) work just fine. For unknown codes, you'll either get "unused" (such as "420 unused") or "500 Internal Server Error" if you go too far (such as 499).

A friendly warning

As mentioned by AlBundyLoves69, using an undocumented feature is dangerous as it will likely break your code in the future. I'm not going to use it anyway, because I won't be able to do this:

header("HTTP/1.0 404 This is not the page you're looking for");

Or something more serious, for instance, if one can't find a resource at /api/resource/1234:

header("HTTP/1.0 404 Resource ID 1234 not found");

As a confirmation that the server received the request correctly.

But exploring is fun for me and I want to share what I found. More feedbacks are welcome.

History

• 6^th December, 2015: Original version
• 8^th December, 2015: Updated: added a warning section