Finalstatic $ this keyword in php learning notes _ PHP Tutorial

Finalstatic $ this keyword learning notes in php. In php, the finalstatic $ this keyword is mainly used in classes or objects. Next, I will record my notes on learning finalstatic $ this. For more information, see. In php, the final static $ this keyword is mainly used in classes or objects. next I will record the final static $ this note, for more information, see.

Final keywords

The php final keyword is used before a function or class name, indicating that the function cannot be rewritten or the class cannot be inherited.

1. The final method cannot be rewritten.

If you do not want a method in the class to be overwritten by the quilt class, you only need to add the keyword final before the method, that is, set the final method.

Instance:

The code is as follows:
Class ex1 { Final function fn1 (){ Return "php "; } } Class ex2 extends ex1 { Function fn1 (){ Return "html "; } } $ P = new ex2 (); Echo $ p-> fn1 (); ?>

Methods with the final keyword cannot be overwritten and an error occurs during running.

2. the final class cannot be inherited.

Classes declared with final cannot be inherited; otherwise, an error occurs.

Instance:

The code is as follows:
Final class ex1 { Private $ name; } Class ex2 extends ex1 { Private $ age; } ?>

Static keywords

The php static keyword can be used not only to declare a static variable, but also to declare static attributes or methods in the class to be "class attributes" or "class methods ".

1. after static attributes and methods are declared, the $ this keyword cannot be used for reference in the class. the following two methods can be used for reference:

In the class: self: static member name

Out-of-class: class name: static member name

2. when accessing this class, you can directly use the class name: static member name format without instantiation.

Static attribute instance:

The code is as follows:
Class user { Private static $ count = 10; Private static $ sum = 1; Public function _ construct (){ For ($ I = 1; $ I <11; $ I ++ ){ Self: $ sum = self: $ sum * self: $ count;/* call static variables */ Self: $ count --; } } Public function getCount (){ Return self: $ sum; } } $ User1 = new user (); Echo $ user1-> getCount (); ?>

Static method instance:

The code is as follows:
Class Math { Public static function sum ($ num1, $ num2 ){ Return $ num1 + $ num2; } Public static function product ($ num1, $ num2 ){ Return $ num1 * $ num2; } } $ A = 88; $ B = 100; Echo "the sum of two numbers :"; Echo" "; Echo Math: sum ($ a, $ B ); Echo" "; $ A = 66; $ B = 88; Echo "the product of two numbers is :"; Echo" "; Echo Math: product ($ a, $ B ); ?>

$ This keyword

To solve the naming conflicts and uncertainty between variables and attributes in php classes and objects, the "$ this" keyword is introduced to call the current object.

You must use the "$ this->" keyword to call the attributes and methods of the current object in the class;
$ This indicates the new object created by the constructor;
The local variables in the method do not belong to the object and do not use the $ this keyword.
With the $ this keyword, we can call object attributes or methods in the class.

1. call variables

Instance:

The code is as follows:
Class user { Private $ n; Function _ construct (){ $ Name = "Mike "; Echo $ this-> n = $ name; } } $ P = new user (); ?>

2. call method

Instance:

The code is as follows:
Class cal { Public function sum ($ a, $ B ){ Return $ a + $ B; } Public function prt ($ a, $ c ){ Return $ a * $ c; } Public function result ($ a, $ B, $ c ){ $ A = $ this-> sum ($ a, $ B ); Return $ this-> prt ($ a, $ c ); } } $ C = new cal (); Echo "(2 + 3) * 10 =". $ c-> result ('2', '3', '10 '); ?>

The static $ this keyword is mainly used in classes or objects. next I will record my final static $ this Notes. For more information, see. Fin...