Description:
------------
---
From manual page: http://www.php.net/function.json-encode#refsect1-function.json-encode-returnvalues
---
It states "Return Values

Returns a JSON encoded string on success or FALSE on failure."

Except, when input is NULL, it returns NULL, not FALSE.

Ref. bug #49588 where the following comment is made:
" [2012-07-02 16:58 UTC] gudjonj at gmail dot com

To return null if encoding is incorrect makes no sense."

This is not a duplicate - this is expressly for NULL as input (all other bug reports involve special characters/local issues).  However, the comment is correct - returning NULL [for any reason] if encoding makes no sense.

Test script:
---------------
$a = NULL;
$b = FALSE;
$c = array("Hello","world!");

var_dump(json_encode($a));

var_dump(json_encode($b));

var_dump(json_encode($c));


Expected result:
----------------
When encoding NULL, FALSE is the expected output (not just because it makes sense, but because the documentation says so ;-)   ).

Actual result:
--------------
NULL