Dependency Injection with PHP and PHP 5.3
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Dependency Injection with PHP and PHP 5.3 Presentation Transcript

  • 1. Dependency Injection with PHP and PHP 5.3 Fabien Potencier
  • 2. Fabien Potencier •  Serial entrepreneur and developer by passion •  Founder of Sensio (in 1998) –  A services and consulting company specialized in Web technologies and Internet marketing (France and USA) –  70 people –  Open-Source specialists –  Big corporate customers –  Consulting, training, development, web design, … and more –  Sponsor of a lot of Open-Source projects like symfony and Doctrine
  • 3. Fabien Potencier •  Creator and lead developer of symfony… •  and creator and lead developer of some more OSS: –  symfony components –  Swift Mailer : Powerful component based mailing library for PHP –  Twig : Fexible, fast, and secure template language for PHP –  Pirum : Simple PEAR Channel Server Manager –  Sismo : PHP continuous integration server –  Lime : Easy to use unit testing library for PHP –  Twitto : A web framework in a tweet –  Twittee : A Dependency Injection Container in a tweet –  Pimple : A small PHP 5.3 dependency injection container
  • 4. Fabien Potencier •  Read my technical blog: http://fabien.potencier.org/ •  Follow me on Twitter: @fabpot •  Fork my code on Github: http://github.com/fabpot/
  • 5. Dependency Injection A real world « web » example
  • 6. In most web applications, you need to manage the user preferences –  The user language –  Whether the user is authenticated or not –  The user credentials –  …
  • 7. This can be done with a User object –  setLanguage(), getLanguage() –  setAuthenticated(), isAuthenticated() –  addCredential(), hasCredential() –  ...
  • 8. The User information need to be persisted between HTTP requests We use the PHP session for the Storage
  • 9. class SessionStorage { function __construct($cookieName = 'PHP_SESS_ID') { session_name($cookieName); session_start(); } function set($key, $value) { $_SESSION[$key] = $value; } // ... }
  • 10. class User { protected $storage; function __construct() Very hard to { customize $this->storage = new SessionStorage(); } function setLanguage($language) { $this->storage->set('language', $language); } // ... } Very easy to use $user = new User();
  • 11. class User { protected $storage; Very easy to customize function __construct($storage) { $this->storage = $storage; } } $storage = new SessionStorage(); $user = new User($storage); Slightly more difficult to use
  • 12. That’s Dependency Injection Nothing more
  • 13. Let’s understand why the first example is not a good idea
  • 14. I want to change the session cookie name
  • 15. class User { protected $storage; function __construct() Hardcode it in the { User class $this->storage = new SessionStorage('SESSION_ID'); } function setLanguage($language) { $this->storage->set('language', $language); } // ... } $user = new User();
  • 16. class User { protected $storage; function __construct() { $this->storage = new SessionStorage(STORAGE_SESSION_NAME); } } Add a global configuration? define('STORAGE_SESSION_NAME', 'SESSION_ID'); $user = new User();
  • 17. class User { protected $storage; function __construct($sessionName) { $this->storage = new SessionStorage($sessionName); } } $user = new User('SESSION_ID'); Configure via User?
  • 18. class User { protected $storage; function __construct($storageOptions) { $this->storage = new SessionStorage($storageOptions ['session_name']); $user = new User( array('session_name' => 'SESSION_ID') ); Configure with an array?
  • 19. I want to change the session storage implementation Filesystem MySQL Memcached …
  • 20. class User { protected $storage; function __construct() Use a global { registry object? $this->storage = Registry::get('session_storage'); } } $storage = new SessionStorage(); Registry::set('session_storage', $storage); $user = new User();
  • 21. Now, the User depends on the Registry
  • 22. Instead of harcoding the Storage dependency inside the User class constructor Inject the Storage dependency in the User object
  • 23. class User { protected $storage; function __construct($storage) { $this->storage = $storage; } } $storage = new SessionStorage('SESSION_ID'); $user = new User($storage);
  • 24. What are the advantages?
  • 25. Use different Storage strategies
  • 26. class User { protected $storage; function __construct($storage) { $this->storage = $storage; } } Use a different Storage engine $storage = new MySQLSessionStorage('SESSION_ID'); $user = new User($storage);
  • 27. Configuration becomes natural
  • 28. class User { protected $storage; function __construct($storage) { $this->storage = $storage; } } Configuration is natural $storage = new MySQLSessionStorage('SESSION_ID'); $user = new User($storage);
  • 29. Wrap third-party classes (Interface / Adapter)
  • 30. class User { protected $storage; Add an interface function __construct(SessionStorageInterface $storage) { $this->storage = $storage; } } interface SessionStorageInterface { function get($key); function set($key, $value); }
  • 31. Mock the Storage object (for testing)
  • 32. class User { protected $storage; function __construct(SessionStorageInterface $storage) { $this->storage = $storage; } } Mock the Session class SessionStorageForTests implements SessionStorageInterface { protected $data = array(); static function set($key, $value) { self::$data[$key] = $value; } }
  • 33. Use different Storage strategies Configuration becomes natural Wrap third-party classes (Interface / Adapter) Mock the Storage object (for testing) Easy without changing the User class
  • 34. « Dependency Injection is where components are given their dependencies through their constructors, methods, or directly into fields. » http://www.picocontainer.org/injection.html
  • 35. $storage = new SessionStorage(); // constructor injection $user = new User($storage); // setter injection $user = new User(); $user->setStorage($storage); // property injection $user = new User(); $user->storage = $storage;
  • 36. A slightly more complex web example
  • 37. $request = new Request(); $response = new Response(); $storage = new FileSessionStorage('SESSION_ID'); $user = new User($storage); $cache = new FileCache( array('dir' => dirname(__FILE__).'/cache') ); $routing = new Routing($cache);
  • 38. class Application { function __construct() { $this->request = new WebRequest(); $this->response = new WebResponse(); $storage = new FileSessionStorage('SESSION_ID'); $this->user = new User($storage); $cache = new FileCache( array('dir' => dirname(__FILE__).'/cache') ); $this->routing = new Routing($cache); } } $application = new Application();
  • 39. Back to square 1
  • 40. class Application { function __construct() { $this->request = new WebRequest(); $this->response = new WebResponse(); $storage = new FileSessionStorage('SESSION_ID'); $this->user = new User($storage); $cache = new FileCache( array('dir' => dirname(__FILE__).'/cache') ); $this->routing = new Routing($cache); } } $application = new Application();
  • 41. We need a Container Describes objects and their dependencies Instantiates and configures objects on-demand
  • 42. A container SHOULD be able to manage any PHP object (POPO) The objects MUST not know that they are managed by a container
  • 43. •  Parameters –  The SessionStorageInterface implementation we want to use (the class name) –  The session name •  Objects –  SessionStorage –  User •  Dependencies –  User depends on a SessionStorageInterface implementation
  • 44. Let’s build a simple container with PHP 5.3
  • 45. DI Container Managing parameters
  • 46. class Container { protected $parameters = array(); public function setParameter($key, $value) { $this->parameters[$key] = $value; } public function getParameter($key) { return $this->parameters[$key]; } }
  • 47. Decoupling $container = new Container(); Customization $container->setParameter('session_name', 'SESSION_ID'); $container->setParameter('storage_class', 'SessionStorage'); $class = $container->getParameter('storage_class'); $sessionStorage = new $class($container->getParameter('session_name')); $user = new User($sessionStorage); Objects creation
  • 48. class Container Using PHP { magic methods protected $parameters = array(); public function __set($key, $value) { $this->parameters[$key] = $value; } public function __get($key) { return $this->parameters[$key]; } }
  • 49. Interface is cleaner $container = new Container(); $container->session_name = 'SESSION_ID'; $container->storage_class = 'SessionStorage'; $sessionStorage = new $container->storage_class($container->session_name); $user = new User($sessionStorage);
  • 50. DI Container Managing objects
  • 51. We need a way to describe how to create objects, without actually instantiating anything! Anonymous functions to the rescue!
  • 52. Anonymous Functions / Lambdas A lambda is a function defined on the fly with no name function () { echo 'Hello world!'; };
  • 53. Anonymous Functions / Lambdas A lambda can be stored in a variable $hello = function () { echo 'Hello world!'; };
  • 54. Anonymous Functions / Lambdas And then it can be used as any other PHP callable $hello(); call_user_func($hello);
  • 55. Anonymous Functions / Lambdas You can also pass a lambda as an argument to a function or method function foo(Closure $func) { $func(); } foo($hello);
  • 56. Fonctions anonymes $hello = function ($name) { echo 'Hello '.$name; }; $hello('Fabien'); call_user_func($hello, 'Fabien'); function foo(Closure $func, $name) { $func($name); } foo($hello, 'Fabien');
  • 57. DI Container Managing objects
  • 58. class Container { protected $parameters = array(); protected $objects = array(); public function __set($key, $value) { $this->parameters[$key] = $value; } public function __get($key) Store a lambda { return $this->parameters[$key]; able to create the object on-demand } public function setService($key, Closure $service) { $this->objects[$key] = $service; } public function getService($key) Ask the closure to create { return $this->objects[$key]($this); th e object and pass the } } current Container
  • 59. $container = new Container(); $container->session_name = 'SESSION_ID'; Description $container->storage_class = 'SessionStorage'; $container->setService('user', function ($c) { return new User($c->getService('storage')); }); $container->setService('storage', function ($c) { return new $c->storage_class($c->session_name); }); Creating the User is now as easy as before $user = $container->getService('user');
  • 60. class Container { protected $values = array(); Simplify the code function __set($id, $value) { $this->values[$id] = $value; } function __get($id) { if (is_callable($this->values[$id])) { return $this->values[$id]($this); } else { return $this->values[$id]; } } }
  • 61. $container = new Container(); Unified interface $container->session_name = 'SESSION_ID'; $container->storage_class = 'SessionStorage'; $container->user = function ($c) { return new User($c->storage); }; $container->storage = function ($c) { return new $c->storage_class($c->session_name); }; $user = $container->user;
  • 62. DI Container Scope
  • 63. For some objects, like the user, the container must always return the same instance
  • 64. spl_object_hash($container->user) !== spl_object_hash($container->user)
  • 65. $container->user = function ($c) { static $user; if (is_null($user)) { $user = new User($c->storage); } return $user; };
  • 66. spl_object_hash($container->user) === spl_object_hash($container->user)
  • 67. $container->user = $container->asShared(function ($c) { return new User($c->storage); });
  • 68. A closure is a lambda that remembers the context of its creation…
  • 69. class Article { public function __construct($title) { $this->title = $title; } public function getTitle() { return $this->title; } } $articles = array( new Article('Title 1'), new Article('Title 2'), );
  • 70. $mapper = function ($article) { return $article->getTitle(); }; $titles = array_map($mapper, $articles);
  • 71. $method = 'getTitle'; $mapper = function ($article) use($method) { return $article->$method(); }; $method = 'getAuthor'; $titles = array_map($mapper, $articles);
  • 72. $mapper = function ($method) { return function ($article) use($method) { return $article->$method(); }; };
  • 73. $titles = array_map($mapper('getTitle'), $articles); $authors = array_map($mapper('getAuthor'), $articles);
  • 74. $container->user = $container->asShared(function ($c) { return new User($c->storage); });
  • 75. function asShared(Closure $lambda) { return function ($container) use ($lambda) { static $object; if (is_null($object)) { $object = $lambda($container); } return $object; }; }
  • 76. class Container { protected $values = array(); function __set($id, $value) { $this->values[$id] = $value; } function __get($id) { Error management if (!isset($this->values[$id])) { throw new InvalidArgumentException(sprintf('Value "%s" is not defined.', $id)); } if (is_callable($this->values[$id])) { return $this->values[$id]($this); } else { return $this->values[$id]; } } }
  • 77. class Container { protected $values = array(); function __set($id, $value) { $this->values[$id] = $value; } function __get($id) { if (!isset($this->values[$id])) { throw new InvalidArgumentException(sprintf('Value "%s" is not defined.', $id)); } if (is_callable($this->values[$id])) { return $this->values[$id]($this); } else { return $this->values[$id]; } } function asShared($callable) { 40 LOC for a fully- return function ($c) use ($callable) { static $object; if (is_null($object)) { $object = $callable($c); featured container } return $object; }; } }
  • 78. More about Dependency Injection http://fabien.potencier.org/article/17/on-php-5-3-lambda-functions-and-closures http://components.symfony-project.org/dependency-injection/ http://github.com/fabpot/pimple http://twittee.org/
  • 79. Twittee: A Container in a tweet •  Implementation does not use PHP 5.3 •  Its usage needs PHP 5.3 class Container { protected $s=array(); function __set($k, $c) { $this->s[$k]=$c; } function __get($k) { return $this->s[$k]($this); } } twittee.org
  • 80. Remember, most of the time, you don’t need a Container to use Dependency Injection
  • 81. You can start to use and benefit from Dependency Injection today
  • 82. by implementing it in your projects by using externals libraries that already use DI without the need of a container
  • 83. Symfony Zend Framework ezComponents Doctrine Swift Mailer …
  • 84. Questions? My slides will be available on slideshare.com/fabpot
  • 85. symfony-live.com with Matthew Weier O’Pheinney I will reveal the first alpha release of Symfony 2.0!
  • 86. symfony-live.com with Matthew Weier O’Pheinney … with Matthew Weier O'Phinney as a special guest
  • 87. Sensio S.A. 92-98, boulevard Victor Hugo 92 115 Clichy Cedex FRANCE Tél. : +33 1 40 99 80 80 Contact Fabien Potencier fabien.potencier at sensio.com http://www.sensiolabs.com/ http://www.symfony-project.org/ http://fabien.potencier.org/
  • 88. BONUS Symfony Components Dependency Injection
  • 89. SymfonyComponentsDependencyInjection
  • 90. DI Container Hello World example use SymfonyComponentsDependencyInjectionBuilder; use SymfonyComponentsDependencyInjectionReference; $container = new Builder(); $container->register('output', 'FancyOutput'); $container-> register('message', 'Message')-> setArguments(array(new Reference('output'), array('with_newline' => true))) ; $container->message->say('Hello World!');
  • 91. $message = $container->message; Get the configuration for the message service The Message constructor must be given an output service Get the output object from the container Create a Message object by passing the constructor arguments
  • 92. $message = $container->message; is roughly equivalent to $output = new FancyOutput(); $message = new Message($output, array('with_newline' => true));!
  • 93. $container = new Builder(); $container->register('output', 'FancyOutput'); $container-> register('message', 'Message')-> setArguments(array(new Reference('output'), array('with_newline' => true))) ; $container->message->say('Hello World!'); PHP <container xmlns="http://symfony-project.org/2.0/container"> <services> XML <service id="output" class="FancyOutput" /> <service id="message" class="Message"> XML is validated <argument type="service" id="output" /> against an XSD <argument type="collection"> <argument key="with_newline">true</argument> </argument> </service> </services> </container> $container = new Builder(); $loader = new XmlFileLoader($container); $loader->load('services.xml');
  • 94. $container = new Builder(); $container->register('output', 'FancyOutput'); $container-> register('message', 'Message')-> setArguments(array(new sfServiceReference('output'), array('with_newline' => true))) ; $container->message->say('Hello World!'); PHP services: output: { class: FancyOutput } message: YAML class: Message arguments: - @output - { with_newline: true } $container = new Builder(); $loader = new YamlFileLoader($container); $loader->load('services.yml');
  • 95. <container xmlns="http://symfony-project.org/2.0/container"> <parameters> <parameter key="output.class">FancyOutput</parameter> <parameter key="message.options" type="collection"> <parameter key="with_newline">true</parameter> </parameter> </parameters> <services> <service id="output" class="%output.class%" /> <service id="message" class="Message"> <argument type="service" id="output" /> <argument>%message.options%</argument> </service> </services> </container> $container = new Builder(); $loader = new XmlFileLoader($container); $loader->load('services.xml');
  • 96. <container xmlns="http://symfony-project.org/2.0/container"> <imports> <import resource="config.xml" /> </imports> <services> <service id="output" class="%output.class%" /> <service id="message" class="Message"> <argument type="service" id="output" /> <argument>%message.options%</argument> </service> </services> </container> <container xmlns="http://symfony-project.org/2.0/container"> <parameters> <parameter key="output.class">FancyOutput</parameter> <parameter key="message.options" type="collection"> <parameter key="with_newline">true</parameter> </parameter> </parameters> </container> $container = new Builder(); $loader = new FileXmlFileLoader($container); $loader->load('services.xml');
  • 97. <services> <import resource="config.yml" class="SymfonyComponentsDependencyInjection LoaderYamlFileLoader" /> <service id="output" class="%output.class%" /> <service id="message" class="Message"> <argument type="service" id="output" /> <argument>%message.options%</argument> </service> </services> parameters: output.class: FancyOutput message.options: { with_newline: true } $container = new Builder(); $loader = new XmlFileLoader($container); $loader->load('services.xml');
  • 98. Loaders & Dumpers •  IniFileLoader •  XmlFileLoader •  YamlFileLoader •  XmlDumper •  YamlDumper Make your container •  PhpDumper VERY fast •  GraphvizDumper
  • 99. use SymfonyComponentsDependencyInjectionBuilder; use SymfonyComponentsDependencyInjectionReference; use SymfonyComponentsDependencyInjectionDumperXmlDumper; use SymfonyComponentsDependencyInjectionDumperYamlDumper; use SymfonyComponentsDependencyInjectionDumperPhpDumper; use SymfonyComponentsDependencyInjectionLoaderXmlFileLoader; use SymfonyComponentsDependencyInjectionLoaderYamlFileLoader; $container = new Builder(); $container->register('output', 'FancyOutput'); $container-> register('message', 'Message')-> setArguments(array(new Reference('output'), array('with_newline' => true))) ;
  • 100. $dumper = new XmlDumper($container); file_put_contents(__DIR__.'/container.xml', $dumper->dump()); $loader = new XmlFileLoader($container); $loader->load(__DIR__.'/container.xml'); $dumper = new YamlDumper($container); file_put_contents(__DIR__.'/container.yml', $dumper->dump()); $loader = new YamlFileLoader($container); $loader->load(__DIR__.'/container.yml'); $dumper = new PhpDumper($container); echo $dumper->dump();
  • 101. use SymfonyComponentsDependencyInjectionContainer; use SymfonyComponentsDependencyInjectionReference; use SymfonyComponentsDependencyInjectionParameter; class ProjectServiceContainer extends Container { protected $shared = array(); protected function getOutputService() { if (isset($this->shared['output'])) return $this->shared['output']; $instance = new FancyOutput(); return $this->shared['output'] = $instance; } protected function getMessageService() { if (isset($this->shared['message'])) return $this->shared['message']; $instance = new Message($this->getService('output'), array('with_newline' => true)); return $this->shared['message'] = $instance; } }
  • 102. use SymfonyComponentsDependencyInjectionDumperGraphvizDumper; $dumper = new GraphvizDumper($container); echo $dumper->dump();
  • 103. digraph sc { ratio="compress" node [fontsize="11" fontname="Arial" shape="record"]; edge [fontsize="9" fontname="Arial" color="grey" arrowhead="open" arrowsize="0.5"]; node_output [label="outputnFancyOutputn", shape=record, fillcolor="#eeeeee", style="filled"]; node_message [label="messagenMessagen", shape=record, fillcolor="#eeeeee", style="filled"]; node_service_container [label="service_containernSymfonyComponentsDependencyInjectionBuilder n", shape=record, fillcolor="#9999ff", style="filled"]; node_message -> node_output [label="" style="filled"]; }