#gRPC Basics: PHP
This tutorial provides a basic PHP programmer's introduction to working with gRPC. By walking through this example you'll learn how to:
It assumes a passing familiarity with protocol buffers. Note that the example in this tutorial uses the proto2 version of the protocol buffers language.
Also note that currently you can only create clients in PHP for gRPC services - you can find out how to create gRPC servers in our other tutorials, e.g. Node.js.
This isn't a comprehensive guide to using gRPC in PHP: more reference documentation is coming soon.
With gRPC you can define your service once in a .proto file and implement clients and servers in any of gRPC's supported languages, which in turn can be run in environments ranging from servers inside Google to your own tablet - all the complexity of communication between different languages and environments is handled for you by gRPC. You also get all the advantages of working with protocol buffers, including efficient serialization, a simple IDL, and easy interface updating.
The example code for our tutorial is in examples/php/route_guide. To download the example, clone this repository by running the following command:
$ git clone https://github.com/grpc/grpc.git
Then change your current directory to examples/php/route_guide
:
$ cd examples/php/route_guide
Our example is a simple route mapping application that lets clients get information about features on their route, create a summary of their route, and exchange route information such as traffic updates with the server and other clients.
You also should have the relevant tools installed to generate the client interface code (and a server in another language, for testing). You can obtain the latter by following these setup instructions.
To try the sample app, we need a gRPC server running locally. Let's compile and run, for example, the Node.js server in this repository:
$ cd ../../node $ npm install $ cd route_guide $ nodejs ./route_guide_server.js --db_path=route_guide_db.json
Run the PHP client (in a different terminal):
$ ./run_route_guide_client.sh
The next sections guide you step-by-step through how this proto service is defined, how to generate a client library from it, and how to create a client stub that uses that library.
First let's look at how the service we're using is defined. A gRPC service and its method request and response types using protocol buffers. You can see the complete .proto file for our example in examples/protos/route_guide.proto
.
To define a service, you specify a named service
in your .proto file:
service RouteGuide { ... }
Then you define rpc
methods inside your service definition, specifying their request and response types. Protocol buffers let you define four kinds of service method, all of which are used in the RouteGuide
service:
// Obtains the feature at a given position. rpc GetFeature(Point) returns (Feature) {}
stream
keyword before the response type.// Obtains the Features available within the given Rectangle. Results are // streamed rather than returned at once (e.g. in a response message with a // repeated field), as the rectangle may cover a large area and contain a // huge number of features. rpc ListFeatures(Rectangle) returns (stream Feature) {}
stream
keyword before the request type.// Accepts a stream of Points on a route being traversed, returning a // RouteSummary when traversal is completed. rpc RecordRoute(stream Point) returns (RouteSummary) {}
stream
keyword before both the request and the response.// Accepts a stream of RouteNotes sent while a route is being traversed, // while receiving other RouteNotes (e.g. from other users). rpc RouteChat(stream RouteNote) returns (stream RouteNote) {}
Our .proto file also contains protocol buffer message type definitions for all the request and response types used in our service methods - for example, here's the Point
message type:
// Points are represented as latitude-longitude pairs in the E7 representation // (degrees multiplied by 10**7 and rounded to the nearest integer). // Latitudes should be in the range +/- 90 degrees and longitude should be in // the range +/- 180 degrees (inclusive). message Point { int32 latitude = 1; int32 longitude = 2; }
The PHP client stub implementation of the proto files can be generated by the protoc-gen-php
tool. To install the tool:
$ cd examples/php $ php composer.phar install $ cd vendor/datto/protobuf-php $ gem install rake ronn $ rake pear:package version=1.0 $ sudo pear install Protobuf-1.0.tgz
To generate the client stub implementation .php file:
$ cd php/route_guide $ protoc-gen-php -i . -o . ./route_guide.proto
A route_guide.php
file will be generated in the php/route_guide
directory. You do not need to modify the file.
To load the generated client stub file, simply require
it in your PHP application:
require dirname(__FILE__) . '/route_guide.php';
The file contains:
examples\RouteGuideClient
that lets clients call the methods defined in the RouteGuide
service.In this section, we'll look at creating a PHP client for our RouteGuide
service. You can see our complete example client code in examples/php/route_guide/route_guide_client.php.
To call service methods, we first need to create a client object, an instance of the generated RouteGuideClient
class. The constructor of the class expects the server address and port we want to connect to:
$client = new examples\RouteGuideClient(new Grpc\BaseStub('localhost:50051', []));
Now let's look at how we call our service methods.
Calling the simple RPC GetFeature
is nearly as straightforward as calling a local asynchronous method.
$point = new examples\Point(); $point->setLatitude(409146138); $point->setLongitude(-746188906); list($feature, $status) = $client->GetFeature($point)->wait();
As you can see, we create and populate a request object, i.e. an examples\Point
object. Then, we call the method on the stub, passing it the request object. If there is no error, then we can read the response information from the server from our response object, i.e. an examples\Feature
object.
print sprintf("Found %s \n at %f, %f\n", $feature->getName(), $feature->getLocation()->getLatitude() / COORD_FACTOR, $feature->getLocation()->getLongitude() / COORD_FACTOR);
Now let's look at our streaming methods. Here's where we call the server-side streaming method ListFeatures
, which returns a stream of geographical Feature
s:
$lo_point = new examples\Point(); $hi_point = new examples\Point(); $lo_point->setLatitude(400000000); $lo_point->setLongitude(-750000000); $hi_point->setLatitude(420000000); $hi_point->setLongitude(-730000000); $rectangle = new examples\Rectangle(); $rectangle->setLo($lo_point); $rectangle->setHi($hi_point); $call = $client->ListFeatures($rectangle); // an iterator over the server streaming responses $features = $call->responses(); foreach ($features as $feature) { // process each feature } // the loop will end when the server indicates there is no more responses to be sent.
The $call->responses()
method call returns an iterator. When the server sends a response, a $feature
object will be returned in the foreach
loop, until the server indiciates that there will be no more responses to be sent.
The client-side streaming method RecordRoute
is similar, except there we pass the method an iterator and get back a examples\RouteSummary
.
$points_iter = function($db) { for ($i = 0; $i < $num_points; $i++) { $point = new examples\Point(); $point->setLatitude($lat); $point->setLongitude($long); yield $point; } }; // $points_iter is an iterator simulating client streaming list($route_summary, $status) = $client->RecordRoute($points_iter($db))->wait();
Finally, let's look at our bidirectional streaming RPC routeChat()
. In this case, we just pass a context to the method and get back a BidiStreamingCall
stream object, which we can use to both write and read messages.
$call = $client->RouteChat();
To write messages from the client:
foreach ($notes as $n) { $route_note = new examples\RouteNote(); $call->write($route_note); } $call->writesDone();
To read messages from the server:
while ($route_note_reply = $call->read()) { // process $route_note_reply }
Each side will always get the other's messages in the order they were written, both the client and server can read and write in any order — the streams operate completely independently.