Namespaces and Autoloading (ZendCon 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. ZendCon October 29th, 2014 Namespaces and Autoloading @beausimensen beau.io joind.in/12075
2. Namespaces
3. since 5.3.0
4. What problems do namespaces solve?
5. COLLISIONS
6. class Highlander { }
7. THERE CAN BE ONLY ONE
8. # class User { } include "src/user.inc"; ! # class User { } include "vendor/3rd-party/lib/user.php" ! PHP Fatal error: Cannot redeclare class User
9. Commodity Names User Item Session Factory! List Client Post Entry Server Log! Cache Logger Input Command! ...
10. Traditional Solutions
11. AcmeUser
12. sfUser
13. PEAR_User
14. Disadvantages
15. What if you have more than one [thing] in your project?
16. AcmeAccountUser! AcmeGroupUser
17. sfAccountUser! sfGroupUser
18. PEAR_Account_User! PEAR_Group_User
19. People tried to organize class names like this
20. It tended to lead to very deep class naming hierarchies
21. substrate_stones_factory _IStoneClassLoaderAware
22. Blech
23. Extremely long class names can be found throughout most legacy PHP projects
24. We've exposed another use case for namespaces
25. OrG a nI Za Tion
26. So namespaces really help solve two problems
27. Collision Prevention and Organization
28. How?
29. \
30. The \ is used to separate namespaces from classes and other namespaces
31. AcmeAccountUser AcmeGroupUser
32. Acme\Account\User Acme\Group\User
33. –Anyone who has ever programmed “But isn't \ the string escape character?”
34. "Acme\Account\User" "Acme\Group\User"
35. "Acme\Account\User" "Acme\Group\User"
36. \\
37. "Acme\\Account\\User" "Acme\\Group\\User"
38. { "autoload": { "psr-0": { "Dflydev\\Cilex\\Provider\\DoctrineOrm\\": "src", "Dflydev\\Pimple\\Provider\\DoctrineOrm\\": "src", "Dflydev\\Silex\\Provider\\DoctrineOrm\\": "src" } } }
39. Using \ can be awkward, but it is better than some of the alternatives that were considered
40. (really, PHP?) :)
41. ... :>
42. (designing a language is hard) ** ^^ %% :::
43. The namespace Keyword
44. Namespaces must be declared before any other code (except for declare)
45. More than one namespace can be declared in the same file
46. namespace Acme; class User { }
47. Acme\User namespace Acme class User
48. namespace Acme\Account; class User { }
49. Acme\Account\User namespace Acme\Account class User
50. You cannot tell just by looking if a string represents a namespace or a class
51. Acme\Account\User Acme\Account\User\Acl Acme\Account\User\Group
52. 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?");
53. It can seem arbitrary and confusing
54. It helps to think of namespaces representing a filesystem
55. helps to think of namespace representing a filesystem
56. PHP does not care where you put your namespaces and classes on disk!
57. But if you use a filesystem as an analogy for namespaces...
58. The namespace keyword tells you where you are in the filesystem
59. namespace Acme\Account; class User { } ! $ cd Acme/Account $ touch User.php ! # Acme/Account/User.php
60. namespace Acme\Account; throw new Exception\SomeError("hi"); ! $ cd Acme/Account $ cat Exception/SomeError.php ! # Acme/Account/Exception/SomeError.php
61. namespace Acme\Account; throw new Exception("wait, what?"); ! $ cd Acme/Account $ cat Exception.php ! # Acme/Account/Exception.php
62. namespace Acme\Account; throw new \Exception("oh, i see!"); ! $ cd Acme/Account $ cat /Exception.php ! # Exception.php
63. $user = new Acme\Account\User(); ! $ cat Acme/Account/User.php ! # Acme/Account/User.php
64. $user = new \Acme\Account\User(); ! $ cat Acme/Account/User.php ! # Acme/Account/User.php
65. How do namespaces address the [incredibly long class name here] problem mentioned earlier?
66. The use Keyword
67. Namespaces and classes can be imported into a file or namespace
68. namespace Acme\Store\Controller; ! use Acme\Account\User; ! $user = new User(); ! # User = Acme\Account\User
69. namespace Acme\Store\Controller; ! use Acme\Account; ! $user = new Account\User();
70. namespace Acme\Store\Controller; ! use Acme\Account\Errors; ! throw new Errors\AccountPastDue();
71. Two namespaces or classes of the same name cannot be imported by use at the same time
72. namespace Acme\Store\Controller; ! use Acme\Account\Errors; use Acme\PayPalClient\Errors; ! PHP Fatal error: Cannot use Acme \PayPalClient\Errors as Errors because the name is already in use
73. namespace Acme\Store\Controller; ! use Acme\Account\Errors; use Acme\PayPalClient\Errors; ! PHP Fatal error: Cannot use Acme \PayPalClient\Errors as Errors because the name is already in use
74. Namespaces and classes can be aliased when they are imported
75. namespace Acme\Store\Controller; ! use Acme\Account\Errors as AccountErrors; use Acme\PayPalClient\Errors as PayPalErrors; ! if ($user->isBad()) { throw new AccountErrors\BadUser( "you know what you did" ); } try { $paypal->tryToCharge($user); } catch (PayPalErrors\TransactionError $e) { throw new AccountErrors\TransportError($e); }
76. namespace Acme\Store; ! use Silex\Controller as BaseController; ! class Controller extends BaseController { }
77. namespace Acme\Account\User; ! use Exception; ! throw new Exception("yay!"); ! # Exception.php
78. 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?");
79. Autoloading
80. Just use your classes
81. # Acme\User is not defined ! $user = new Acme\User(); ! # Acme\User is defined
82. Magic!
83. You probably won't use most of what you are about to learn directly... (it is good history to know, though!)
84. __autoload since 5
85. The __autoload function is called anytime a class does not exist
86. function __autoload($class) { if ($class === "Acme\\Account\\User") { // do something to cause this class // to become defined require __DIR__."/src/user.inc"; } }
87. The major limitation of __autoload is that it is only one function
88. spl_autoload_register since 5.1.2
89. With spl_autoload_register more than one autoloader implementation can be registered at the same time
90. spl_autoload_register( // Registers Acme's autoloader Acme::autoloader ); ! spl_autoload_register( // Registers Doctrine's autoloader Doctrine::autoloader ); ! spl_autoload_register(function($class) { // Register a rarely used class if ($class === "Acme\\RarelyUsed\\User") { require __DIR__."/src/user.inc"; } });
91. It's a stack!
92. Don't write an autoloader
93. Use an off-the-shelf autoloader
95. This means you will have to follow an autoloading standard
96. PSR-0
97. PHP-FIG PHP Framework Interoperability Group
98. PSR-0 Autoloading Standard
99. –Larry Garfield "For sufficiently vague definitions of 'accepted', May 2009 is the date I use."
100. Remember the filesystem analogy?
101. PSR-0 essentially codified that concept and made it a thing
102. Namespaces become directories
103. Classes become files with .php suffix
104. Acme\Account\User
105. Acme/Account/User.php
106. PSR-0 also supports legacy PEAR style naming conventions
107. Acme\Account\User ! Acme_Account_User
108. Acme/Account/User.php ! Acme/Account/User.php
109. Legacy rules are kinda convoluted
110. _ is converted to / but only in the class name
111. Acme\Web_Site\User_Controller
112. Acme/Web_Site/User/Controller.php
113. PSR-0 had a handful of other relatively insignificant* issues * the significance of the issues varies wildly depending on who you ask
114. PSR-0 was widely adopted by PHP-FIG member projects
115. This led to PSR-0 being widely adopted
117. { "autoload": { "psr-0": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php
118. { "autoload": { "psr-0": { "Acme_Account_": "src" } } } ! new Acme_Account_User(); ! # src/Acme/Account/User.php
119. DEPRECATED!
120. PSR-4
121. PHP-FIG PHP Framework Interoperability Group
122. PSR-4 Autoloading Standard Dec 3rd, 2013
123. Overall same idea as PSR-0 in that it maintains a direct relationship between namespaces and the filesystem
124. Only supports namespaces and does not support legacy naming conventions
125. Introduces a namespace prefix and a base directory for mapping
126. Acme\Account\User (class) ! Acme\Account (namespace prefix) ! src (base directory) ! src/User.php (resulting file path)
127. The namespace prefix and base directory were influenced by widespread Composer adoption
128. Trimming the "extra directories" addressed some people's complaints about PSR-0
129. Dropping support for legacy naming simplified PSR-4 autoloader implementations
131. { "autoload": { "psr-4": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/User.php
132. PHP-FIG now recommends PSR-4 over PSR-0
133. [this page intentionally left blank]
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
138. PSR-4 > PSR-0
139. { "autoload": { "psr-0": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php
140. { "autoload": { "psr-4": { "Acme\\Account\\": "src/Acme/Account" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php
142. joind.in/12075 Questions? @beausimensen • beau.io @thatpodcast • thatpodcast.io ddd.io/zendcon2014-namespaces
143. Beau Simensen @beausimensen beau.io
144. #composer look for simensen and say "hi" freenode IRC
145. dflydev @dflydev dflydev.com
146. boogio.com @wearboogio reflxlabsinc.com @reflxlabs