Several program examples of PHP static methods_PHP tutorial

The rules for static methods are the same as static variables. Use the ststic keyword to identify a method as a static method, which can be accessed through the name of the class and the scope qualification operator::.

A very important difference between static methods and non-static methods is that when calling static methods, we do not need to create an instance of the class.

Program List: Use class name as parameter

Using class names as parameters can solve non-inherited static problems.

  
<?php
class Fruit {
	public static $category = "I'm fruit";
    
    static function find($class) 
	{
    	$vars = get_class_vars($class) ;
      	echo $vars['category'] ;
    }
}
class Apple extends Fruit {
     public static $category = "I'm Apple";
}
Apple::find("Apple");
?>

Program execution result:

I'm Apple

Program List: Overriding base class methods

Override the base class method in the derived class.

  
<?php
class Fruit
{
	static function Foo ( $class = __CLASS__ )
   	{
       	call_user_func(array($class, 'Color'));
   	}
}
class Apple extends Fruit
{
   	static function Foo ( $class = __CLASS__ )
   	{
       	parent::Foo($class);
   	}
   	static function Color()
   	{
       	echo "Apple's color is red";
   	}
}
Apple::Foo(); // This time it works.
?>

Program execution result:

Apple's color is red

Program List: Use of static arrays

Both static and const scopes can be accessed using the :: operator. If you want to use the :: operator to access an array, you need to declare the array as static in advance.

  
<?php
class Fruit
{
  	static $color = array('color1' => 'red', 'color2' => 'yellow');
}
class Apple
{
  	public function __construct()
  	{
    	var_dump(Fruit::$color);
  	}
}
class Banana
{
  public function __construct()
  {
    Fruit::$color = FALSE;
  }
}
new Apple();    // prints array(2) { ["color1"]=> string(3) "red" ["color2"]=> string(6) "yellow" } 
echo '<br />';
new Banana();
new Apple();    // prints bool(false)
?>

Program execution result:

array(2) { ["color1"]=> string(3) "red" ["color2"]=> string(6) "yellow" } 
bool(false)

Program List: Another singleton pattern

Static is really cool, the program below demonstrates how to get an already existing instance.

    
<?php
class Singleton {
    private static $instance=null;
    private $value=null;
    private function __construct($value) {
        $this->value = $value;
    }
    public static function getInstance() {
        if ( self::$instance == null ) {
            echo "<br>new<br>";
            self::$instance = new Singleton("values");
        }  
		else {
            echo "<br>old<br>";
        }
        return self::$instance;
    }
}
$x = Singleton::getInstance();
var_dump($x); // returns the new object
$y = Singleton::getInstance();
var_dump($y); // returns the existing object
?>

Program execution result:

new
object(Singleton)#1 (1) { ["value:private"]=> string(6) "values" } 
old
object(Singleton)#1 (1) { ["value:private"]=> string(6) "values" }

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