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protobuf-php/protobuf
=====================

PHP implementation of Google's Protocol Buffers

v0.1.3(9y ago)2701.4M—2.3%33[5 issues](https://github.com/protobuf-php/protobuf/issues)[1 PRs](https://github.com/protobuf-php/protobuf/pulls)17MITPHPPHP >=5.5.0

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Protobuf for PHP
================

[](#protobuf-for-php)

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Protobuf for PHP is an implementation of Google's Protocol Buffers for the PHP language, supporting its binary data serialization and including a `protoc`plugin to generate PHP classes from .proto files.

Installation
------------

[](#installation)

Run the following `composer` commands:

```
$ composer require "protobuf-php/protobuf"
```

Overview
--------

[](#overview)

This tutorial provides a basic introduction to working with protocol buffers. By walking through creating a simple example application, it shows you how to

- Define message formats in a `.proto` file.
- Use the protocol buffer compiler.
- Use the PHP protocol buffer API to write and read messages.

#### Why Use Protocol Buffers?

[](#why-use-protocol-buffers)

The example we're going to use is a very simple "address book" application that can read and write people's contact details to and from a file. Each person in the address book has a name, an ID, an email address, and a contact phone number.

How do you serialize and retrieve structured data like this? There are a few ways to solve this problem:

- Use PHP Serialization. This is the default approach since it's built into the language, but it is not very space efficient, and also doesn't work very well if you need to share data with applications written in other languages (Nodejs,Java,Python, etc..).
- You can invent an ad-hoc way to encode the data items into a single string – such as encoding 4 ints as "12:3:-23:67". This is a simple and flexible approach, although it does require writing one-off encoding and parsing code, and the parsing imposes a small run-time cost. This works best for encoding very simple data.
- Serialize the data to XML. This approach can be very attractive since XML is (sort of) human readable and there are binding libraries for lots of languages. This can be a good choice if you want to share data with other applications/projects. However, XML is notoriously space intensive, and encoding/decoding it can impose a huge performance penalty on applications. Also, navigating an XML DOM tree is considerably more complicated than navigating simple fields in a class normally would be.

Protocol buffers are the flexible, efficient, automated solution to solve exactly this problem. With protocol buffers, you write a `.proto` description of the data structure you wish to store. From that, the protocol buffer compiler creates a class that implements automatic encoding and parsing of the protocol buffer data with an efficient binary format. The generated class provides getters and setters for the fields that make up a protocol buffer and takes care of the details of reading and writing the protocol buffer as a unit. Importantly, the protocol buffer format supports the idea of extending the format over time in such a way that the code can still read data encoded with the old format.

#### Defining Your Protocol Format

[](#defining-your-protocol-format)

To create your address book application, you'll need to start with a `.proto` file. The definitions in a `.proto` file are simple: you add a message for each data structure you want to serialize, then specify a name and a type for each field in the message. Here is the `.proto` file that defines your messages, `addressbook.proto`.

```
package tutorial;
import "php.proto";
option (php.package) = "Tutorial.AddressBookProtos";

message Person {
  required string name = 1;
  required int32 id = 2;
  optional string email = 3;

  enum PhoneType {
    MOBILE = 0;
    HOME = 1;
    WORK = 2;
  }

  message PhoneNumber {
    required string number = 1;
    optional PhoneType type = 2 [default = HOME];
  }

  repeated PhoneNumber phone = 4;
}

message AddressBook {
  repeated Person person = 1;
}
```

As you can see, the syntax is similar to C++ or Java. Let's go through each part of the file and see what it does. The `.proto` file starts with a package declaration, which helps to prevent naming conflicts between different projects. In PHP, the package name is used as the PHP namespace unless you have explicitly specified a `(php.package)`, as we have here. Even if you do provide a `(php.package)`, you should still define a normal package as well to avoid name collisions in the Protocol Buffers name space as well as in non PHP languages.

After the package declaration, you can see two options that are PHP-specific: `import "php.proto";` and `(php.package)`.

- `import "php.proto"` add supports a few PHP specific options for proto files.
- `(php.package)` specifies in what php namespace name your generated classes should live. If you don't specify this explicitly, it simply matches the package name given by the package declaration, but these names usually aren't appropriate PHP namespace names.

Next, you have your message definitions. A message is just an aggregate containing a set of typed fields. Many standard simple data types are available as field types, including `bool`, `int32`, `float`, `double`, and `string`. You can also add further structure to your messages by using other message types as field types – in the above example the `Person` message contains `PhoneNumber` messages, while the `AddressBook` message contains `Person` messages. You can even define message types nested inside other messages – as you can see, the `PhoneNumber` type is defined inside `Person`. You can also define `enum` types if you want one of your fields to have one of a predefined list of values – here you want to specify that a phone number can be one of `MOBILE`, `HOME`, or `WORK`.

The `" = 1"`, `" = 2"` markers on each element identify the unique `tag` that field uses in the binary encoding. Tag numbers 1-15 require one less byte to encode than higher numbers, so as an optimization you can decide to use those tags for the commonly used or repeated elements, leaving tags 16 and higher for less-commonly used optional elements. Each element in a repeated field requires re-encoding the tag number, so repeated fields are particularly good candidates for this optimization.

Each field must be annotated with one of the following modifiers:

- **required**: a value for the field must be provided, otherwise the message will be considered "uninitialized". Trying to build an uninitialized message will throw a RuntimeException. Parsing an uninitialized message will throw an IOException. Other than this, a required field behaves exactly like an optional field.
- **optional**: the field may or may not be set. If an optional field value isn't set, a default value is used. For simple types, you can specify your own default value, as we've done for the phone number type in the example. Otherwise, a system default is used: zero for numeric types, the empty string for strings, false for bools. For embedded messages, the default value is always the "default instance" or "prototype" of the message, which has none of its fields set. Calling the accessor to get the value of an optional (or required) field which has not been explicitly set always returns that field's default value.
- **repeated**: the field may be repeated any number of times (including zero). The order of the repeated values will be preserved in the protocol buffer. Think of repeated fields as dynamically sized arrays.

You'll find a complete guide to writing .proto files – including all the possible field types – in the [Protocol Buffer Language Guide](https://developers.google.com/protocol-buffers/docs/proto). Don't go looking for facilities similar to class inheritance, though – protocol buffers don't do that.

#### Compiling Your Protocol Buffers

[](#compiling-your-protocol-buffers)

Now that you have a `.proto`, the next thing you need to do is generate the classes you'll need to read and write `AddressBook` (and hence `Person` and `PhoneNumber`) messages. To do this, you need to run the protocol buffer plugin on your .proto:

If you haven't installed the compiler (`protoc`) or you dont have the php plugin, see .

Now run the compiler plugin, specifying the proto files source directory (the file directory is used if you don't provide a value), the destination directory (where you want the generated code to go), and the path to your `.proto` In this case:

```
php ./vendor/bin/protobuf --include-descriptors -i . -o ./src/ ./addressbook.proto
```

This generates the following PHP classes in your specified destination directory

```
src/
└── Tutorial
    └── AddressBookProtos
        ├── AddressBook.php
        ├── Person
        │   ├── PhoneNumber.php
        │   └── PhoneType.php
        └── Person.php
```

#### The Protocol Buffer API

[](#the-protocol-buffer-api)

Let's look at some of the generated code and see what classes and methods the compiler has created for you. If you look in `src/Tutorial/AddressBookProtos/Person.php` you can see that it defines a class called `Person`.

Messages have auto-generated accessor methods for each field of the message. Here are some of the accessors for the Person class (implementations omitted for brevity):

```

```

As you can see, there are simple getters and setters for each field. There are also has getters for each singular field which return true if that field has been set. Repeated fields have a extra method, an add method which appends a new element to the list.

Notice how these accessor methods use camel-case naming, even though the `.proto` file uses lowercase-with-underscores. This transformation is done automatically by the protocol buffer compiler so that the generated classes match standard PHP style conventions. You should always use lowercase-with-underscores for field names in your `.proto` files; this ensures good naming practice in all the generated languages. See the style guide for more on good `.proto` style.

Protocol Buffers types map to the following PHP types:

Protocol BuffersPHPdoublefloatfloatfloatint32intint64intuint32intuint64intsint32intsint64intfixed32intfixed64intsfixed32intsfixed64intboolboolstringstringbytes\\Protobuf\\Stream#### Enums and Nested Classes

[](#enums-and-nested-classes)

The generated code includes a `PhoneType` [enum](https://github.com/protobuf-php/protobuf/blob/master/src/Enum.php):

```

```

All nested types are generated using the parent class `Person` as part of its namespace.

```