Namespaces and Autoloading (Madison PHP 2014)

Want to make sure that your class names don't overwrite the class names for any other projects on the server? Hate having long class names like [insert ridiculously long classname here]? Namespaces were introduced in PHP 5.3 to help address these common issues. Learn how to namespace classes and see how namespaces and class autoloading can make your coding experience much nicer!

Transcript

1. Namespaces and Autoloading Madison PHP January 23rd, 2014
2. Beau Simensen @beausimensen beau.io
3. #madisonphp look for simensen and say "hi" freenode irc
4. Dragonfly Development @dflydev dflydev.com
5. Namespaces
6. since 5.3.0
7. What problems do namespaces solve?
8. COLLISIONS
9. class Highlander { }
10. THERE CAN BE ONLY ONE
11. # class User { } include "src/user.inc"; ! # class User { } include "vendor/3rd-party/lib/user.php" ! PHP Fatal error: Cannot redeclare class User
12. Commodity Names User Item Session Factory! List Client Post Entry Server Log! Cache Logger Input Command! ...
13. Traditional Solutions
14. AcmeUser
15. sfUser
16. PEAR_User
17. Disadvantages
18. What if you have more than one [thing] in your project?
19. AcmeAccountUser! AcmeGroupUser
20. sfAccountUser! sfGroupUser
21. PEAR_Account_User! PEAR_Group_User
22. People tried to organize class names like this
23. It tended to lead to very deep class naming hierarchies
24. substrate_stones_factory _IStoneClassLoaderAware
25. Blech
26. Extremely long class names can be found throughout most legacy PHP projects
27. We've exposed another use case for namespaces
28. OrG a nI Za Tion
29. So namespaces really help solve two problems
30. Collision Prevention and Organization
31. How?
32. \
33. The \ is used to separate namespaces from classes and other namespaces
34. AcmeAccountUser AcmeGroupUser
35. Acme\Account\User Acme\Group\User
36. –Anyone who has ever programmed “But isn't \ the string escape character?”
37. "Acme\Account\User" "Acme\Group\User"
38. "Acme\Account\User" "Acme\Group\User"
39. \\
40. "Acme\\Account\\User" "Acme\\Group\\User"
41. { "autoload": { "psr-0": { "Dflydev\\Cilex\\Provider\\DoctrineOrm\\": "src", "Dflydev\\Pimple\\Provider\\DoctrineOrm\\": "src", "Dflydev\\Silex\\Provider\\DoctrineOrm\\": "src" } } }
42. Using \ can be awkward, but it is better than some of the alternatives that were considered
43. (really, PHP?) :)
44. ... :>
45. (designing a language is hard) ** ^^ %% :::
46. The namespace Keyword
47. Namespaces must be declared before any other code (except for declare)
48. More than one namespace can be declared in the same file
49. namespace Acme; class User { }
50. Acme\User namespace Acme class User
51. namespace Acme\Account; class User { }
52. Acme\Account\User namespace Acme\Account class User
53. You cannot tell just by looking if a string represents a namespace or a class
54. Acme\Account\User Acme\Account\User\Acl Acme\Account\User\Group
55. namespace Acme\Account; ! use Acme\Account\User; ! class User { public static function err($message) { throw new User\Exception\SomeError($message); } } ! namespace Acme\Account\User\Exception; ! class SomeError extends \Exception { } ! \Acme\Account\User::err("Confused Yet?");
56. It can seem arbitrary and confusing
57. It helps to think of namespaces representing a filesystem
58. helps to think of namespace representing a filesystem
59. PHP does not care where you put your namespaces and classes on disk!
60. But if you use a filesystem as an analogy for namespaces...
61. The namespace keyword tells you where you are in the filesystem
62. namespace Acme\Account; class User { } ! $ cd Acme/Account $ touch User.php ! # Acme/Account/User.php
63. namespace Acme\Account; throw new Exception\SomeError("hi"); ! $ cd Acme/Account $ cat Exception/SomeError.php ! # Acme/Account/Exception/SomeError.php
64. namespace Acme\Account; throw new Exception("wait, what?"); ! $ cd Acme/Account $ cat Exception.php ! # Acme/Account/Exception.php
65. namespace Acme\Account; throw new \Exception("oh, i see!"); ! $ cd Acme/Account $ cat /Exception.php ! # Exception.php
66. $user = new Acme\Account\User(); ! $ cat Acme/Account/User.php ! # Acme/Account/User.php
67. $user = new \Acme\Account\User(); ! $ cat Acme/Account/User.php ! # Acme/Account/User.php
68. How do namespaces address the [incredibly long class name here] problem mentioned earlier?
69. The use Keyword
70. Namespaces and classes can be imported into a file or namespace
71. namespace Acme\Store\Controller; ! use Acme\Account\User; ! $user = new User(); ! # User = Acme\Account\User
72. namespace Acme\Store\Controller; ! use Acme\Account; ! $user = new Account\User();
73. namespace Acme\Store\Controller; ! use Acme\Account\Errors; ! throw new Errors\AccountPastDue();
74. Two namespaces or classes of the same name cannot be imported by use at the same time
75. namespace Acme\Store\Controller; ! use Acme\Account\Errors; use Acme\PayPalClient\Errors; ! PHP Fatal error: Cannot use Acme \PayPalClient\Errors as Errors because the name is already in use
76. namespace Acme\Store\Controller; ! use Acme\Account\Errors; use Acme\PayPalClient\Errors; ! PHP Fatal error: Cannot use Acme \PayPalClient\Errors as Errors because the name is already in use
77. Namespaces and classes can be aliased when they are imported
78. namespace Acme\Store\Controller; ! use Acme\Account\Errors as AccountErrors; use Acme\PayPalClient\Errors as PayPalErrors; ! if ($user->isBad()) { throw new AccountErrors\BadUser( "you know what you did" ); } try { $paypal->tryToCharge($user); } catch (PayPalErrors\TransactionError $e) { throw new AccountErrors\TransportError($e); }
79. namespace Acme\Store; ! use Silex\Controller as BaseController; ! class Controller extends BaseController { }
80. namespace Acme\Account\User; ! use Exception; ! throw new Exception("yay!"); ! # Exception.php
81. namespace Acme\Account; ! use Acme\Account\User; ! class User { public static function err($message) { throw new User\Exception\SomeError($message); } } ! namespace Acme\Account\User\Exception; ! class SomeError extends \Exception { } ! \Acme\Account\User::err("A little less confusing?");
82. Autoloading
83. Just use your classes
84. # Acme\User is not defined ! $user = new Acme\User(); ! # Acme\User is defined
85. Magic!
86. You probably won't use most of what you are about to learn directly... (it is good history to know, though!)
87. __autoload since 5
88. The __autoload function is called anytime a class does not exist
89. function __autoload($class) { if ($class === "Acme\\Account\\User") { // do something to cause this class // to become defined require __DIR__."/src/user.inc"; } }
90. The major limitation of __autoload is that it is only one function
91. spl_autoload_register since 5.1.2
92. With spl_autoload_register more than one autoloader implementation can be registered at the same time
93. spl_autoload_register( // Registers Acme's autoloader Acme::autoloader ); ! spl_autoload_register( // Registers Doctrine's autoloader Doctrine::autoloader ); ! spl_autoload_register(function($class) { // Register a rarely used class if ($class === "Acme\\RarelyUsed\\User") { require __DIR__."/src/user.inc"; } });
94. It's a stack!
95. Don't write an autoloader
96. Use an off-the-shelf autoloader
98. This means you will have to follow an autoloading standard
99. PSR-0
100. PHP-FIG PHP Framework Interoperability Group
101. PSR-0 Autoloading Standard
102. –Larry Garfield "For sufficiently vague definitions of 'accepted', May 2009 is the date I use."
103. Remember the filesystem analogy?
104. PSR-0 essentially codified that concept and made it a thing
105. Namespaces become directories
106. Classes become files with .php suffix
107. Acme\Account\User
108. Acme/Account/User.php
109. PSR-0 also supports legacy PEAR style naming conventions
110. Acme\Account\User ! Acme_Account_User
111. Acme/Account/User.php ! Acme/Account/User.php
112. Legacy rules are kinda convoluted
113. _ is converted to / but only in the class name
114. Acme\Web_Site\User_Controller
115. Acme/Web_Site/User/Controller.php
116. PSR-0 had a handful of other relatively insignificant* issues * the significance of the issues varies wildly depending on who you ask
117. PSR-0 was widely adopted by PHP-FIG member projects
118. This led to PSR-0 being widely adopted
120. { "autoload": { "psr-0": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php
121. { "autoload": { "psr-0": { "Acme_Account_": "src" } } } ! new Acme_Account_User(); ! # src/Acme/Account/User.php
122. PSR-4
123. PHP-FIG PHP Framework Interoperability Group
124. PSR-4 Autoloading Standard Dec 3rd, 2013
125. Overall same idea as PSR-0 in that it maintains a direct relationship between namespaces and the filesystem
126. Only supports namespaces and does not support legacy naming conventions
127. Introduces a namespace prefix and a base directory for mapping
128. Acme\Account\User (class) ! Acme\Account (namespace prefix) ! src (base directory) ! src/User.php (resulting file path)
129. The namespace prefix and base directory were influenced by widespread Composer adoption
130. Trimming the "extra directories" addressed some people's complaints about PSR-0
131. Dropping support for legacy naming simplified PSR-4 autoloader implementations
133. { "autoload": { "psr-4": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/User.php
134. So, namespaces and autoloading...
135. Namespaces are useful for collision prevention and organization
136. Don't write an autoloader
137. Use an autoloading standard
139. Questions? @beausimensen beau.io