Status response objects are needed mostly to make it possible from the
client perspective to differentiate a status response with the payload
"OK" from a normale bulk reply containing "OK".
The biggest change is for commands returning +OK responses: these were
previously translated to TRUE (bool value), but they are now returned
as instances of Predis\Response\Status. Just to illustrate an example
of the possibilities with this change we will use SET since it is the
most widely used command returning +OK:
$response = $client->set('foo', 'bar');
echo $response; // 'OK'
$response == 'OK'; // TRUE
isset($response->ok); // TRUE
$response == true; // TRUE
$response === true; // FALSE
$response instanceof Predis\Response\ObjectInterface; // TRUE
$response instanceof Predis\Response\Status; // TRUE
For those checking responses returned by commands such as SET or PONG,
the breaking change basically lies in the usage of strict comparison:
doing $response === true will now evaluate to FALSE instead of TRUE.
By default Predis caches common status responses such as OK or QUEUED
to lower the memory usage when using pipelines or transactions.
Connection classes should just handle, convert and return simple Redis
types while parsing and transforming structured replies should be done
by consumers (see Predis\Client or Predis\Transaction\MultiExecContext).
This actually makes more sense considering that parsing a complex response
with the associated command parser may require different actions. As an
example, the result of EXEC is a multibulk that holds the actual responses,
so we really need to parse each one of its elements and we should also
make sure that iterable multibulks are consumed. We already did that
previously, but it was weird knowing that command parsers were applied
by the connection class.
This also moves some duplicated logic away from each connection class
implementation which is a nice bonus.
The "throw_errors" connection parameter has been removed and replaced by the
new "exceptions" client option since exceptions on -ERR replies returned by
Redis are not generated by connection classes anymore but are thrown by the
client class and other abstractions such as pipeline contexts.
This change does not affect much people using the Predis\Client class (aside
from the different configuration) but gives much more flexibility to those
building their own pieces of code around the internal classes of Predis.
Daniele Alessandri