A better ServiceDescriptionLoader for Guzzle 3.x

v2.0 2016-01-21 15:31 UTC


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A better ServiceDescriptionLoader for Guzzle 3.x


Guzzle's service descriptions make it easy to describe APIs. A service description takes the form of a JSON object (or PHP associative array) that describes all the available operations and data models supported by the API. However, for large or poorly-designed APIs, the service description can quickly become hard to manage.

This project offers a replacement ServiceDescriptionLoader implementation, which allows for much more flexibility when writing service descriptions. It supports:

  • Separating the service description arbitrarily into many files ("modular" service descriptions)
  • Alternative formats (plain text and YAML)


To get this library in to an existing project, the best way is to use Composer.

  1. Add bradfeehan/guzzle-modular-service-descriptions as a Composer dependency in your project's composer.json file:

        "require": {
            "bradfeehan/guzzle-modular-service-descriptions": "~1.0"
  2. If you haven't already, download and install Composer:

    $ curl -sS | php
  3. Install your Composer dependencies:

    $ php composer.phar install
  4. Set up Composer's autoloader:

    require_once 'vendor/autoload.php';


In contrast to typical Guzzle service descriptions, a modular service description is implemented as a directory. The format of the directory is very flexible. The directory structure is reflected in the heirarchy of the service description data.


A file in the root of a modular service description directory defines the key with the name of the file. The content of the file defines the value of that key. As an example, consider the following directory structure:

├── name.txt
└── operations.json

The my_service_description directory can be loaded as a modular service description. The content inside name.txt will be put into the key name at the top level of the service description. The content of operations.json will be the value for the operations key in the service description. (So, to be a valid service description, operations.json should contain a JSON object, defining all the operations).

Nested directories

Another, more complex example:

├── name.txt
└── operations/
    ├── ComplexOperation/
    │   └── parameters.yml
    └── ComplexOperation.json

Again, name.txt will contain the value for the name key. However, this time, the operations key is represented by a directory. The files inside are converted to nested keys in the resulting service description. So this example will result in the following representation:

    "name": "[content of name.txt]",
    "operations": {
        "ComplexOperation": {
            // The keys defined in ComplexOperation.json
            // will be inserted here
            // ...
            "parameters": "[parsed content of parameters.yml]"
__index files

Any files named __index.[ext] define the contents of the directory the file is in, rather than the name of the file. It's essentially an "empty" name. This concept is similar to Python's, which makes the directory the package, rather than the file.


Files can also be grouped without causing the contents to be nested. This is useful for organising a large service description. For example, if there are thousands of operations, you'd have to have that many files in the operations directory. Using groups, the operations can be grouped logically inside the operations directory.

A group is implemented as a directory ending with .group. So you could have containing all the operations relating to users, etc.

Note that this could cause problems if you wanted to have a key ending with .group. Please let me know by filing a GitHub issue if this causes you any issues, and we can work out a way to compromise.

Loading the service description

To load a modular service description, load it using the included loader, and add it to the web service client instance:

use BradFeehan\GuzzleModularServiceDescriptions\ServiceDescriptionLoader;
use Guzzle\Service\Client;

// Create a client somehow
$client = Client::factory();

// Instantiate the modular service description loader
$loader = new ServiceDescriptionLoader();

// Point the loader at the modular service description directory
$description = $loader->load('/path/to/service_description');

// Add the service description to the client

// Done!
$command = $client->getCommand('MyCommand');

// ...