json_encode() used a peculiar way of apply-count management,
whereby the apply-count was not incremented for the outermost
object/array, so that recursion was only detected after two
levels.
json_encode() no longer throws warnings. Instead only the error code for
json_last_error() is set.
As it is hard to debug the error from just an error code an optional
$as_string parameter was added to json_last_error(), which returns an
error message instead of an error code.
json_encode() now returns bool(false) for all possible errors, throws the
respective warning and also sets the respective json_last_error() error
code. Three new error codes have been added:
* JSON_ERROR_RECURSION
* JSON_ERROR_INF_OR_NAN
* JSON_ERROR_UNSUPPORTED_TYPE
To get a partial JSON output instead of bool(false) the option
JSON_PARTIAL_OUTPUT_ON_ERROR can be specified. In this case the invalid
segments will be replaced either by null (for recursion, unsupported type
and invalid JSON) or 0 (for Inf and NaN).
The warning for invalid UTF-8 stays intact and is thrown also with
display_errors = On. If this behavior is undesired this can be remedied
later.
