PHP classes, interfaces, overloading related knowledge example code summary

This article mainly introduces the relevant knowledge points of the PHP class, and summarizes and analyzes the final class, final method, abstract class## related to the PHP class in the form of examples. #, abstract methods, interfaces, overloading, Magic methods and other related concepts and operating techniques, friends in need can refer to the following

The examples in this article summarize the relevant knowledge points of PHP classes. Share it with everyone for your reference, the details are as follows:

Final class and final method

If a method in the parent class is declared final, the subclass cannot override it method. If a class is declared final, it cannot be inherited.

final class a{}
class a{
  final public function A(){}
}

Abstract class and abstract method

abstract class a {
  public abstract function func();
}
class A extends a{
  public function func(){}
}

① A class can be declared as an abstract class using abstract; an abstract class is a class that cannot be instantiated, only Be the parent class of other classes.

abstract class name{}

② A method can be declared as an abstract method using abstract; abstract methods only need to declare the method header and do not need the method body in the curly brackets.

abstract public function name($val);

③ If there is an abstract method in a class, the class must be declared as an abstract class.

④ If a subclass inherits from an abstract class, the subclass cannot implement all abstract methods in the parent class unless the subclass also continues to be an abstract class.

⑤ When a subclass implements a method of an abstract parent class, the scope of the access control character cannot be reduced, and the parameters of the method must also be consistent (rewritten).

Interface

Interface can be regarded as a higher level abstraction of abstract class, it can be said to be a special case of abstract class

interface a{
  function func();
}
class A implements a {
  function func(){}
}

Class: attributes, class constants, methods

Abstract class: attributes, class constants, abstract methods

Interface: interface constants, abstract methods

① Compared with abstraction Classes and interfaces can implement 'multiple inheritance'

class A implements a,b,c{}

② An interface can only inherit one interface

interface a extends b{}

③ The methods are all abstract methods No abstract modification is required, that is, the lower-level class either implements the interface's methods (implements) or declares it as an abstract method

Overloading technology

1 . Attribute overloading: If a non-existent attribute is used, a predefined method in the class will be called to process the data;

For application scenarios where attributes are not used, do the following processing

① Value: Automatically call get() in the class② Assignment: Automatically call set() in the class
③ Determine whether it exists: Automatically call isset()# in the class ##④ Destruction: Automatically call unset() in the class

The premise is that these methods are predefined, otherwise an error will be reported

<?php
class bee{
  public $ol = array();
  public function get($key){
    if(isset($this->ol[$key])){
      return $this->ol[$key];
    }
    return $key.&#39; not exists&#39;;
  }
  public function set($key,$val){
    $this->ol[$key] = $val;
  }
  public function isset($key){
    if(isset($this->ol[$key])){
      return true;
    }
    return false;
  }
  public function unset($key){
    unset($this->ol[$key]);
  }
}
$obj = new bee();
echo $obj->one;
echo &#39;<br>&#39;;
$obj->one = 1;
echo $obj->one;
echo &#39;<br>&#39;;
var_dump(isset($obj->one));

The running results are as follows:

one not exists
1
boolean true

2.

Method overloading: If a method that does not exist is used, a predefined method in the class will be called to handle the behavior; For application scenarios where methods are not used, do the following processing

① Call inaccessible methods in objects: call()

② Call inaccessible methods in static mode: callStatic()

<?php
class bee{
  public function call($name,$arr){
    echo &#39;<br>&#39;;
    echo &#39;function &#39;.$name.&#39; not exist&#39;;
  }
  static function callStatic($name,$arr){
    echo &#39;<br>&#39;;
    echo &#39;function &#39;.$name.&#39; not exist&#39;;
  }
  /*public function call($name,$arr){
    $num = count($arr);
    if($num<1){
      $name();
    }else{
      $name = $name.&#39;_one&#39;;
      $name($arr[0]);
    }
  }*/
}
$obj->func();
bee::staFunc();
/*$obj->func(1);
function func(){
  echo &#39;<br>&#39;;
  echo &#39;no.0&#39;;
}
function func_one($val){
  echo &#39;<br>&#39;;
  echo &#39;no.&#39;.$val;
}*/

The running results are as follows:

function func not exist
function staFunc not exist

Note: The above methods are all magic methods with parameters

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