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Summary of examples of PHP related knowledge points

高洛峰
高洛峰Original
2016-12-21 13:54:571028browse

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

Final class and final method

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

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

Abstract classes and abstract methods

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 and is only used as a parent class for 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 braces.

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 access control scope cannot be reduced, and the method parameters 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 abstract classes, 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 without abstract modification, that is, the lower-level classes either implement the interface methods (implements) or are also declared as abstract methods

Overloading technology

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

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

① Value: Automatically call __get() in the class
② Assignment: Automatically call __get() in the class __set()
③ Determine whether it exists: automatically call __isset()
④ in the class Destruction: automatically call __unset() in the class

The premise is that these methods are pre-defined, 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;

It is not used for methods For application scenarios, 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

I hope this article will be helpful to everyone in PHP programming.

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