Using PHP 5.3 Namespaces for Fame and Fortune

Using PHP 5.3 Namespaces
for Fame and Fortune
Matthew Weier O'Phinney
Project Lead, Zend Framework

© All rights reserved. Zend Technologies, Inc.

What are “namespaces”?


What are “namespaces”?

"A way in which to group
related classes, functions and constants"
– http://php.net/namespace


Basics


Namespace Separator

“”
Get over it!


What can live in namespaces
● Classes
● Constants
● Functions


Declaring namespaces
● Single line declaration
namespace Foo;


Declaring namespaces
● Block declaration
namespace Foo
{
}
namespace Bar
{
}


Subnamespaces
● Separate the subnamespaces using the
namespace separator
namespace FooBar;

namespace FooBarBaz;


Referring to namespaced elements
● From non-namespaced code:
$class = new FooBarClass();
$class = new FooBarBazClass();
FoobarFunc(); // function call
$val = FooBAT; // constant value


● From code using the same namespace:
namespace Foo;

$class = new BarClass();
$class = new BarBazClass();
barFunc(); // function call
$val = BAT; // constant value


● From code in a different namespace:
namespace Bar;

$class = new FooBarClass();
$class = new FooBarBazClass();
FoobarFunc(); // function call
$val = FooBAT; // constant value


Using namespaced code:
● Prefixing with a namespace separator resolves
as a fully qualified name
● Resolution order:
▶ Globally qualified: known; otherwise:
▶ Current namespace, or relative to it
(Classes, functions, constants)
▶ Global namespace
(functions, constants)


Importing namespaces
● A way to bring code from another namespace
into the current namespace.
● Import:
▶ Classes
▶ Other namespaces
● Keyword used is use


Importing namespaces

namespace Foo;
class Bar {}

namespace Bar;
use Foo; // imports namespace
use FooBar; // imports class


Using imported code

namespace Bar;
use Foo; // imports namespace
$bar = new FooBar();

namespace Bar;
use FooBar; // imports class
$bar = new Bar();


Aliasing
● "import namespace or class, but refer to it
using this name"
● PHP utilizes the as keyword to alias


Aliasing

namespace Bar;
use Foo as f;
$bar = new fBar();

namespace Bar;
use FooBar as bar;
$bar = new bar();


Make typehinting more semantic!

namespace App;
use ZendEventManagerEventManager as Events;

class Foo
{
public function events(Events $events = null)
{
if ($events instanceof Events) {
$this->events = $events;
} elseif (!$this->events instanceof Events) {
$this->events = new Events(__CLASS__);
}
return $this->events;
}
}


Importing multiple namespaces/classes
● Multiple use statements
namespace BazBat;
use Foo;
use Bar;


● Or use a comma (“,”) to separate statements
namespace BazBat;
use Foo,
Bar;


● With aliases
namespace BazBat;

use Foo as f, // aliased
Bar; // not aliased


What namespace are you in?
● __NAMESPACE__


Comprehensive example
● The setup:
namespace FooBar;
const BAZ = 1;
function baz($data) {}
class Baz {}

namespace FooBaz;
const BAZ = 2;
function baz($data) {}
class Baz {}


Comprehensive example
namespace Test;
use FooBarBaz as BarBaz,
FooBaz;

const BAZ = 3;
echo BAZ; // 3
echo BazBAZ; // 2
echo FooBarBAZ; // 1

$baz = new BarBaz(); // FooBarBaz
$baz = new Baz(); // E_FATAL (no matching class)
$baz = new BazBaz(); // FooBazBaz

baz($baz); // E_FATAL (no matching function in
// current namespace)
Bazbaz($baz); // FooBazbaz()


Pitfalls


Referencing namespaced code in strings
● Classes, constants, and functions referenced in
a string MUST be fully qualified
● No namespace separator prefix is necessary


● Example 1
namespace Foo;
// Assume FooBarBaz is a defined class

$class = 'BarBaz';
$o = new $class; // E_FATAL; can't find
// relative names

$class = 'FooBarBaz';
$o = new $class; // Success

$o = new $class; // Also success,
// but not necessary


● Example 2
namespace Foo;
// Assume FooBarBaz is a defined class

$class = 'BarBaz';
if ($o instanceof $class) { } // Fails; can't
// resolve class

if ($o instanceof $class) { } // Success


Why use namespaces?


Code Organization: Filesystem
● Namespace separator has an affinity for the
directory separator
● Suggests a 1:1 relationship with file system
namespace FooBar;
class Baz {}
/* Foo/Bar/Baz.php (*nix)
FooBarBaz.php (Windows) */


Code Organization: By Responsibility
● Interfaces
▶ Use cases:
● instanceof: $class instanceof Adapter
● implements: SomeClass implements Adapter
▶ Natural language is easiest to understand
▶ Natural language suggests a hierarchy



namespace ComponentAdapter;
use ComponentAdapter;

class ConcreteAdapter implements Adapter
{}

● interface ComponentAdapter in
Component/Adapter.php
● class ComponentAdapterConcreteAdapter in
Component/Adapter/ConcreteAdapter.php


● Takeaway: we're referencing the capabilities,
not the language type


Readability
● When within a namespace, reference classes
directly, keeping usage succinct
namespace ZendHttp;
$client = new Client();


Readability
● Importing and aliasing make names more
succinct
namespace Application;
use ZendHttpClient as HttpClient,
ZendLoggerLogger;

$client = new HttpClient();
$log = new Logger();


Readability
● Aliasing allows giving names context
namespace ApplicationController;

use ZendControllerAction
as ActionController;

class FooController
extends ActionController {}


Dependency declarations
● Suggestion: import every class outside the
current namespace that you consume
namespace ApplicationController;

use ZendControllerAction
as ActionController,
MyORMMapper as DataMapper,
MyEntityBlogEntry,
ZendEventManagerEventManager;


Dependency declarations
● Imports are hints to the interpreter, and don't
cost anything
● Helps to document dependencies up front
● Allows static analysis to determine
dependencies


Resources


● PHP Manual: http://php.net/namespace


Webinar
To watch the recorded webinar, please go to

http://www.zend.com/en/webinar/Framework/
70170000000bWGR-PHP-Namespaces.flv
or

http://bit.ly/pcVMKR

(a short registration is required)


Using PHP 5.3 Namespaces for Fame and Fortune

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