Dependency Injection (DI) is a fantastic technique, but what if you what to use dependency injection in your legacy application. Fear not! As someone who as done this very thing, I will show how you can successful and incrementally add DI to any application. I will present a number of recipes and solutions to common problems and give a tour of the various PHP DI projects and how they can help.

1. Dependency
Adding
Injection To Legacy
Applications

3. Who Is i3logix?

4. Inversion of Control

5. Dependency Injection

8. Built-In
Flexibility

9. interface Calc {
public function __invoke($left, $right);
}
class AddCalc implements Calc {
public function __invoke($left, $right) {
return $left + $right;
}
}
class SubCalc implements Calc {
public function __invoke($left, $right) {
return $left - $right;
}
}

10. class Calculator{
public function __invoke(Calc $calc, $left, $right){
return $calc($left, $right);
}
}
$calculator = new Calculator();
echo $calculator(new AddCalc(), 2, 1), "n";
echo $calculator(new SubCalc(), 2, 1), "n";

11. De-Coupling

12. Have Clear Goals

14. It’s
only
a
Tool

15. I T
N E
J C
H
E
N
C
I
T
Q
I
U
O
E
N S

17. class Status {
public function get($system) {
$client = new Zend_Http_Client();
$r = $client->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
if ($r->isSuccessful()) {
return $r->getBody();
}
return false;
}
}

18. Constructor
Injection
Vs.
Setter/Property
Injection

19. class StatusSetterInject{
protected $client;
public function setClient(Zend_Http_Client $client){
$this->client = $client;
}
public function get($system){
$r = $this->client->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
if ($r->isSuccessful()){
return $r->getBody();
}
return false;
}
}

20. class StatusConstructInject{
protected $client;
public function __construct(Zend_Http_Client $client){
$this->client = $client;
}
public function get($system){
$r = $this->client->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
if($r->isSuccessful()){
return $r->getBody();
}
return false;
}
}

21. Init Pattern

22. class StatusInit{
protected $client;
public function __construct(Zend_Http_Client $client){
$this->client = $client;
$this->init();
}
public function init(){
//Left empty
}
public function get($system){
$r = $this->client->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
//...
}
}

23. Optional
Injection

24. class StatusConstructInjectOptional{
protected $client;
public function __construct(
Zend_Http_Client $client = null){
if($client === null){
$client = new Zend_Http_Client();
}
$this->client = $client;
}
public function get($system){
$r = $this->client->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
//...
}
}

25. class StatusSetterInjectOptional{
protected $client;
public function setClient(Zend_Http_Client $client){
$this->client = $client;
}
protected function getClient(){
if ($this->client === null){
$this->client = new Zend_Http_Client();
}
return $this->client;
}
public function get($system){
$r = $this->getClient()->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
//...

26. Class Name Override

27. class StatusClassNameOverrideConstruct{
protected $clientClass;
public function __construct($class = 'Zend_Http_Client'){
$this->clientClass = $class;
}
public function get($system){
$client = new $this->clientClass;
$r = $this->getClient()->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
if($r->isSuccessful()){
return $r->getBody();
}
return false;
}
}

28. class StatusClassNameOverrideSetter{
protected $clientClass = 'Zend_Http_Client';
public function setClass($class){
$this->clientClass = $class;
}
public function get($system){
$client = new $this->clientClass;
$r = $this->getClient()->setUri(SERVICE_URI)
->setParameterGet(compact('system'))
->request('GET');
if($r->isSuccessful()){
return $r->getBody();
}
return false;
}
}

29. BUT I NEED TO CREATE OBJECTS?

30. class PolyBad {
public function foo($bar) {
if (get_class($bar) === 'SomeOtherClass') {
$tmp = new SomeClass();
}
}
}

31. class PolyGood {
public function foo(SomeClass $bar) {
if ($baz instanceof SomeInterface) {
// Do something
}
}
}

33. class Factory{
public function create(){
return new SimpleClass();
}
}

34. Dynamic Factory

35. abstract class FactoryAbstract{
protected abstract function getClassName();
public function create(){
$class = $this->getClassName();
$argList = func_get_args();
if (count($argList) < 1){
return new $class;
}
$rClass = new ReflectionClass($class);
return $rClass->newInstanceArgs($argList);
}
}

36. function __autoload($class){
$classPath = str_replace('_', '/', $class);
$filePath = __DIR__."/src/$classPath.php";
if (file_exists($filePath))
return require $filePath;
if (substr($class, -7) !== 'Factory')
return;
$subName = substr($class, 0, -8);
eval("class $class extends FactoryAbstract{
protected function getClassName(){
return '$subName';
}
}");
}

37. WHAT IS INJECTING THESE OBJECTS?

38. Injector, Provider, Container

39. Configuration

40. <service id="bar" class="FooClass" shared="true"
constructor="getInstance">
<file>%path%/foo.php</file>
<argument>foo</argument>
<argument type="service" id="foo" />
<argument type="collection">
<argument>true</argument>
<argument>false</argument>
</argument>
<configurator function="configure" />
<call method="setBar" />
<call method="setBar">
<argument>foo</argument>
<argument type="service" id="foo" />
<argument type="collection">
<argument>true</argument>
<argument>false</argument>
</argument>
</call>
</service>

41. Interfaces

42. if($obj instanceof InjectDb){
$obj->setDb($this->serviceLocator->getDb());
}
if($obj instanceof InjectTool){
$obj->setTool($this->serviceLocator->getTool());
}
if($obj instanceof InjectClientBuilder){
$obj->setClientBuilder($this->getClientBuilder());
}
if($obj instanceof InjectEvent){
$obj->setEvent($this->serviceLocator->getEvent());
}

43. Duck Typing

44. abstract class Zend_View_Abstract
implements Zend_View_Interface
//...
public function registerHelper($helper, $name){
//...
if (!$helper instanceof Zend_View_Interface){
if (!method_exists($helper, $name)){
require_once 'Zend/View/Exception.php';
$e = new Zend_View_Exception(
'View helper must …');
$e->setView($this);
throw $e;
}
}
if (method_exists($helper, 'setView')){
$helper->setView($this);
}
//...

45. Auto Wiring

46. $rParmList = $methodReflection->getParameters();
foreach($rParmList as $rParm ){
$parmClass = $rParm->getClass();
if($parmClass !== null){
$bindConfig->getInjectionConfig()
->addMethodInstanceKey(
$methodName, $parmClass->getName());
}else{
throw new Exception(
"Not possible to configure automatically"
);
}
}

47. Annotations

48. /**
* @Singleton
*/
class LoggerSimple{
/**
* @Inject Zend_Db_Adapter_Abstract
*/
public $db;
/**
* @Inject
* @Arg Zend_Db_Adapter_Abstract
*/
public function __construct($db){
$this->db = $db;
}
/**
* @Inject
* @Arg Zend_Db_Adapter_Abstract
*/
public function setDb($db){
$this->db = $db;
}
}

49. /**
* @ImplementedBy LoggerSimple
*/
interface Logger{
public function log($message, $level);
}

50. $rClass = new ReflectionAnnotatedClass($config->getClass());
if($rClass->isInterface()){
if($rClass->hasAnnotation('ImplementedBy') === false){
throw new Exception(…);
}
$impClass = $rClass->getAnnotation('ImplementedBy')->value;
if($impClass === null){
throw new Exception (…);
}
$config->setImplementationClass($impClass);
}

51. Combine. Win!

53. Singleton

54. class Db{
protected function __construct(){}
protected function __clone(){}
public static function instance(){
static $instance = null;
if($instance === null){
$instance = new static();
}
return $instance;
}
}

55. Singleton + Registry

56. class Registry{
protected static $reg = array();
public static function add($key, $value){
static::$reg[$key] = $value;
}
public static function get($key){
return static::$reg[$key];
}
}

57. class Registry{
protected static $reg = array();
public static function add($key, $value){
static::$reg[$key] = $value;
}
public static function get($key){
$value = static::$reg[$key];
if(is_callable($value)){
return $value();
}
return $value;
}
}

58. Registry::add('db', function (){return new Db();});
var_dump(Registry::get('db'));

59. Service Locator

60. class ServiceLocator{
protected function __construct(){}
protected function __clone(){}
public static function instance(){
static $instance = null;
if($instance === null){
$instance = new static();
}
return $instance;
}
public function getDb(){
static $db = null;
if($db === null){
$db = new Db();
}
return $db;
}
}

61. Coarse-Grained
Fine-Grained

63. Design by
Contract

64. class Logger{}

65. abstract class LoggerAbstract{}
class LoggerEcho extends LoggerAbstract{}
class LoggerFile extends LoggerAbstract{}

66. interface LoggerInterface{}
abstract class LoggerAbstract implements LoggerInterface{}
class LoggerEcho extends LoggerAbstract{}
class LoggerFile extends LoggerAbstract{}
class LoggerOddBall implements LoggerInterface{}

67. class Logger{}

68. abstract class Logger{}
class LoggerEcho extends Logger{}
class LoggerFile extends Logger{}

69. interface Logger{}
abstract class LoggerAbstract implements Logger{}
class LoggerEcho extends Logger{}
class LoggerFile extends Logger{}
class LoggerOddBall implements Logger{}

70. Prefer Composition Over Inheritance

71. WHAT’S ALREADY OUT THERE?

75. YOU NEED
A
GAME PLAN!

77. http://joind.in/3740
T HANK Y OU!