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.
Supporting this feature has been problematic and leaded to some ugly
code to make abstractions such as pipelines and transactions aware of
these kind of response objects. Furthermore, it was not possible to
add them to all the connection classes due to implementation limits.
For such reasons Predis do not support them globally anymore, but the
actual classes are still shipped within the library so that they can
be used to build custom stuff at a level lower than client (that is,
unless we decide to remove them for good before going stable).
This cannot be implemented for previous versions of PHP because we
need socket_import_stream() to extract the underlying socket resource
from the stream in order to be able to set the TCP_NODELAY flag.
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
Alexandru Patranescu