Php functions, classes and objects, class encapsulation, inheritance, class static methods, static attributes, php static

Php functions, classes and objects, class encapsulation, inheritance, class static methods, static attributes, php static

   
1. Functions
    
Php built-in functions can be used directly. If php extensions are not installed
    
Custom Functions
         
// Function name: function dump ($ var = null) {// default expenditure parameter value: echo '<pre/>'; var_dump ($ var );}
    
2. class and object (new Obj)
      
<? Php // defines a Person's class. The class Person is not a private attribute.
    
Private $ eye = 'Big eyes '; private $ mouth = 'small mouth'; private $ leg = 'long legs '; // constructor calls public function _ construct () {echo _ CLASS __;} public function run () {echo $ this-> leg ;} // you can use leg (walking), eye (reading), and mouth (reading) public function study () {echo $ this-> leg, $ this-> eye, $ this-> mouth ;}/// the object $ person = new Person () will become after class new is used; // The output Person $ person-> run (); // output long legs $ person-> study (); // output big legs, big eyes, and small lips
    
3. Class encapsulation (public, protected, private) and inheritance (extends)
      
// Class inheritance class A {public function help () {echo _ METHOD __;}// declare A private function eat () {echo _ METHOD __;}}// subclass can inherit all public methods and attributes of the parent class, protected methods and attributes, except for private methods // if you want to use them, override class B extends A {public function doSomething () {$ this-> help (); // The premise for inheriting the parent class method is to declare it as public echo '    
// Output result
    
A: help
    
 B: eat
4. Static methods and static attributes of Classes
      
<? Php // define a class Url related to a Url {public static function createUrl ($ arr = []) {echo _ METHOD __;} public static function redirect ($ url = '') {echo _ METHOD __;} public static function getCurrentUrl () {echo _ METHOD __;}} // declare the method as a static method. You do not need to instantiate (new) objects every time. This method is easy to operate, saves memory, and is more efficient. echo Url: createUrl ($ var = ''); echo Url: redirect ($ url = ''); echo Url: getCurrentUrl ();
    
5. Static attributes of a class
      
<? Php // define a class Url related to a Url {// declare it as a class constant const URL = 'HTTP: // www.baidu.com '; // After 5.3, you can directly use const outside the class // declare it as a static variable public static $ var = 'it is very good '; public static function createUrl ($ arr = []) {echo self: URL; echo '<br/>'; echo self: $ var; echo '<br/>'; echo _ METHOD __;} public static function redirect ($ url = '') {echo _ METHOD __;} public static function getCurrentUrl () {echo _ METHOD __;}/// declare the METHOD as a static METHOD. You do not need to instantiate (new) objects every time. The operation is convenient, memory saving, and the efficiency is higher. echo Url :: createUrl ($ var = '');