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php[world] November 12th, 2014 Namespaces and Autoloading @beausimensen beau.io joind.in/11864

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Namespaces

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since 5.3.0

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What problems do namespaces solve?

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COLLISIONS

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class Highlander { }

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THERE CAN BE ONLY ONE

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# class User { } include "src/user.inc"; ! # class User { } include "vendor/3rd-party/lib/user.php" ! PHP Fatal error: Cannot redeclare class User

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Commodity Names User Item Session Factory! List Client Post Entry Server Log! Cache Logger Input Command! ...

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Traditional Solutions

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AcmeUser

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sfUser

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PEAR_User

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Disadvantages

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What if you have more than one [thing] in your project?

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AcmeAccountUser! AcmeGroupUser

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sfAccountUser! sfGroupUser

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PEAR_Account_User! PEAR_Group_User

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People tried to organize class names like this

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It tended to lead to very deep class naming hierarchies

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substrate_stones_factory _IStoneClassLoaderAware

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Blech

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Extremely long class names can be found throughout most legacy PHP projects

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We've exposed another use case for namespaces

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OrG a nI Za Tion

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So namespaces really help solve two problems

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How?

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\

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The \ is used to separate namespaces from classes and other namespaces

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AcmeAccountUser AcmeGroupUser

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Acme\Account\User Acme\Group\User

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–Anyone who has ever programmed “But isn't \ the string escape character?”

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"Acme\Account\User" "Acme\Group\User"

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"Acme\Account\User" "Acme\Group\User"

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\\

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"Acme\\Account\\User" "Acme\\Group\\User"

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{ "autoload": { "psr-0": { "Dflydev\\Cilex\\Provider\\DoctrineOrm\\": "src", "Dflydev\\Pimple\\Provider\\DoctrineOrm\\": "src", "Dflydev\\Silex\\Provider\\DoctrineOrm\\": "src" } } }

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Using \ can be awkward, but it is better than some of the alternatives that were considered

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(really, PHP?) :)

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... :>

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(designing a language is hard) ** ^^ %% :::

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The namespace Keyword

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Namespaces must be declared before any other code (except for declare)

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More than one namespace can be declared in the same file

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namespace Acme; class User { }

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Acme\User namespace Acme class User

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namespace Acme\Account; class User { }

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Acme\Account\User namespace Acme\Account class User

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You cannot tell just by looking if a string represents a namespace or a class

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Acme\Account\User Acme\Account\User\Acl Acme\Account\User\Group

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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?");

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It can seem arbitrary and confusing

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It helps to think of namespaces representing a filesystem

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helps to think of namespace representing a filesystem

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PHP does not care where you put your namespaces and classes on disk!

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But if you use a filesystem as an analogy for namespaces...

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The namespace keyword tells you where you are in the filesystem

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namespace Acme\Account; class User { } ! $ cd Acme/Account $ touch User.php ! # Acme/Account/User.php

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namespace Acme\Account; throw new Exception\SomeError("hi"); ! $ cd Acme/Account $ cat Exception/SomeError.php ! # Acme/Account/Exception/SomeError.php

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namespace Acme\Account; throw new Exception("wait, what?"); ! $ cd Acme/Account $ cat Exception.php ! # Acme/Account/Exception.php

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namespace Acme\Account; throw new \Exception("oh, i see!"); ! $ cd Acme/Account $ cat /Exception.php ! # Exception.php

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$user = new Acme\Account\User(); ! $ cat Acme/Account/User.php ! # Acme/Account/User.php

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$user = new \Acme\Account\User(); ! $ cat Acme/Account/User.php ! # Acme/Account/User.php

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How do namespaces address the [incredibly long class name here] problem mentioned earlier?

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The use Keyword

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Namespaces and classes can be imported into a file or namespace

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namespace Acme\Store\Controller; ! use Acme\Account\User; ! $user = new User(); ! # User = Acme\Account\User

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namespace Acme\Store\Controller; ! use Acme\Account; ! $user = new Account\User();

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namespace Acme\Store\Controller; ! use Acme\Account\Errors; ! throw new Errors\AccountPastDue();

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Two namespaces or classes of the same name cannot be imported by use at the same time

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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

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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

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Namespaces and classes can be aliased when they are imported

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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); }

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namespace Acme\Store; ! use Silex\Controller as BaseController; ! class Controller extends BaseController { }

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namespace Acme\Account\User; ! use Exception; ! throw new Exception("yay!"); ! # Exception.php

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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?");

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Autoloading

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Just use your classes

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# Acme\User is not defined ! $user = new Acme\User(); ! # Acme\User is defined

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Magic!

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You probably won't use most of what you are about to learn directly... (it is good history to know, though!)

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__autoload since 5

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The __autoload function is called anytime a class does not exist

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function __autoload($class) { if ($class === "Acme\\Account\\User") { // do something to cause this class // to become defined require __DIR__."/src/user.inc"; } }

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The major limitation of __autoload is that it is only one function

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spl_autoload_register since 5.1.2

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With spl_autoload_register more than one autoloader implementation can be registered at the same time

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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"; } });

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Don't write an autoloader

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Use an off-the-shelf autoloader

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No content

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This means you will have to follow an autoloading standard

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PSR-0

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PHP-FIG PHP Framework Interoperability Group

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PSR-0 Autoloading Standard

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–Larry Garfield "For sufficiently vague definitions of 'accepted', May 2009 is the date I use."

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Remember the filesystem analogy?

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PSR-0 essentially codified that concept and made it a thing

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Namespaces become directories

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Classes become files with .php suffix

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Acme\Account\User

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Acme/Account/User.php

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PSR-0 also supports legacy PEAR style naming conventions

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Acme\Account\User ! Acme_Account_User

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Acme/Account/User.php ! Acme/Account/User.php

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Legacy rules are kinda convoluted

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_ is converted to / but only in the class name

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Acme\Web_Site\User_Controller

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Acme/Web_Site/User/Controller.php

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PSR-0 had a handful of other relatively insignificant* issues * the significance of the issues varies wildly depending on who you ask

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PSR-0 was widely adopted by PHP-FIG member projects

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This led to PSR-0 being widely adopted

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No content

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{ "autoload": { "psr-0": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php

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{ "autoload": { "psr-0": { "Acme_Account_": "src" } } } ! new Acme_Account_User(); ! # src/Acme/Account/User.php

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PSR-0 IS DEPRECATED!

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Nothing. What PSR-0 being deprecated means to you.

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PSR-4

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PHP-FIG PHP Framework Interoperability Group

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PSR-4 Autoloading Standard Dec 3rd, 2013

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Overall same idea as PSR-0 in that it maintains a direct relationship between namespaces and the filesystem

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Only supports namespaces and does not support legacy naming conventions

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Introduces a namespace prefix and a base directory for mapping

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Acme\Account\User (class) ! Acme\Account (namespace prefix) ! src (base directory) ! src/User.php (resulting file path)

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The namespace prefix and base directory were influenced by widespread Composer adoption

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Trimming the "extra directories" addressed some people's complaints about PSR-0

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Dropping support for legacy naming simplified PSR-4 autoloader implementations

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{ "autoload": { "psr-4": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/User.php

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PHP-FIG now recommends PSR-4 over PSR-0

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Namespaces are useful for collision prevention and organization

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Don't write an autoloader

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Use an autoloading standard

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PSR-4 > PSR-0

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{ "autoload": { "psr-0": { "Acme\\Account\\": "src" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php

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{ "autoload": { "psr-4": { "Acme\\Account\\": "src/Acme/Account" } } } ! new Acme\Account\User(); ! # src/Acme/Account/User.php

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No content

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joind.in/11864 Questions? @beausimensen • beau.io @thatpodcast • thatpodcast.io ddd.io/phpworld2014-namespaces

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Beau Simensen @beausimensen beau.io

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#composer look for simensen and say "hi" freenode IRC

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dflydev @dflydev dflydev.com

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boogio.com @wearboogio reflxlabsinc.com @reflxlabs