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82 lines
2.0 KiB
Markdown
82 lines
2.0 KiB
Markdown
When writing a class, all of the properties and methods are being defined for the object
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that will be created from the class.
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```php
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<?php
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class House
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{
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public $color;
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public function __construct($color)
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{
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$this->color = $color;
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}
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}
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```
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Like building a house, a class is a blueprint that
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defines what the house can do and the object is the house itself that can actually
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perform the actions defined in the blueprint.
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```php
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$house = new House('Green');
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```
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However, what if you want the blueprint to have properties and methods?
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That is when you use the `static` keyword. In this class, we will define a default color
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on the class itself and then use it when creating a new object.
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```php
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class Skyscraper
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{
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private static $popularColor;
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public $color;
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public static function setDefaultColor($color)
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{
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self::$popularColor = $color;
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}
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public function __construct()
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{
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$this->color = self::$popularColor;
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}
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}
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```
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You can access static methods and properties using double colons on `self` inside the object
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or on the class name outside of the object. Static methods and properties can only access
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other static methods and properties.
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```php
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Skyscraper::setDefaultColor('Grey');
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$skyscraper = new Skyscraper();
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echo $skyscraper->color . "\n";
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```
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Often, you will see static constructors in PHP.
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A static constructor creates a new instance of an object. Why would do that when you can just use "new Class" to create
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the object? The most common reason is to make the code more readable.
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```php
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class TinyHouse
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{
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private $color;
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private $wheels;
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private $trailer;
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public static function build($color, $wheels, $trailer)
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{
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return new self($color, $wheels, $trailer);
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}
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public function __construct($color, $wheels, $trailer)
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{
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$this->color = $color;
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$this->wheels = $wheels;
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$this->trailer = $trailer;
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}
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}
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```
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Using `build` can make more sense than `new`, but it is ultimately a personal preference.
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```php
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$house = TinyHouse::build('Blue', 4, true);
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```
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