PHP share 22: PHP Object-oriented

1:static Access character

• Using static in a class has two main uses, defining static members, and defining static methods. Static members retain only one variable value, which is valid for all instances
• The method of the class is static, and the property that he accesses must also be static

2:static late Static binding

What is static binding?

Abstract class U {}class u1 extends U {public    static function create () {        return new U1 ()}    } Class U2 extends U {public    static function create () {        return new U2 ();}    }

This piece of code works fine, but a lot of repetitive code can be annoying.

I don't want to add the Create method to each subclass, and if you put the Create method in the superclass U, the code might be

Abstract class u{public    static function create ()    {       //return new self ();  Self will make an error, and self's role in the class is not exactly the same as $this's effect on the object. Self is not referring to the calling context, he refers to the parsing context,
So if you run the above, you'll get
Fatal Error:cannot Instantiate abstract class U in d:wampwwwtestoopstatic.php on line 21
Self is therefore parsed to define the U of Create, rather than the U1 class that resolves to call self.

Static can be used not only for instantiation, but also as a call identifier for a static method, even from a non-static context, as self,parent.
return new Static ();}    } Class U1 extends U{}class U2 extends u{} $res = U1::create (); Var_dump ($res);

Static can be used not only for instantiation, but also as a call identifier for a static method, even from a non-static context, as self,parent.

Abstract class u{    private $group;    Public function __construct ()    {        $this->group = Static::getgroup ();    }    public static function Create ()    {        return new static ();    }    static function Getgroup ()    {        return ' default ';    }} Class U1 extends u{    }class U2 extends u{    static function Getgroup ()    {        return ' U2 ';    }} Class U3 extends u2{    }print_r (U1::create ());

U1 Object ([group:u:private] = default)

U3 Object ([group:u:private] = U2)

Example:

Class A {public    static function foo () {        static::who ();    }     public static function who () {        echo __class__. \ n ";    }} Class B extends A {public    static function test () {        a::foo ();  If you change to static, then bind backwards, and if it is a, the lowest class is a        Parent::foo ();        Self::foo ();    }     public static function who () {        echo __class__. \ n ";    }} Class C extends B {public    static function who () {        echo __class__. \ n ";    }} C::test ();

Output: A c c

PHP share 22: PHP Object-oriented