Examples of overloads in PHP and several common magic methods

In object-oriented languages, there is a very important concept--overload, that is, overloading. Overloading is typically a method for implementing several overloads within a class that have the same names and different parameter forms. In PHP, however, this concept has nothing to do with "overloading" in most object-oriented languages, which is irrelevant at all.

Overloading in PHP refers to the dynamic creation of class properties and methods. Overloaded methods are called when a class property or method is called that is undefined or not visible under the current environment. The straightforward point, then, is a processing mechanism that accesses a class or object's inaccessible properties or methods . (not accessible, such as non-existent or restricted by access to the keyword)

1. Property overloading

Four Magic methods:

1) __get ($ attribute name)

This method is called automatically when accessing an object that is not accessible

2) __set ($ property name, $ property value)

This method is called automatically when a value is assigned to an inaccessible property in an object. The two parameters in the method, which in turn represent the properties that are accessed and the corresponding values.

3) __isset ($ attribute name)

This method is called automatically when a property that is inaccessible to an object is isset () or empty ().

4) __unset ($ attribute name)

This method is called automatically when a property that is inaccessible to an object is unset () destroyed.

The code used is as follows:

<?PHPHeader("Content-type:text/html;charset = Utf-8"); classtest{ Public $p 1= 1; function__get ($property) {//This method is automatically called when access to an inaccessible property      Echo"Inaccessible Properties: {$property}"; }    function__set ($property,$value) {//Assigning a value to an inaccessible property automatically calls the method      Echo"For inaccessible Properties {$property} Assignment {$value}<br/> "; }    function__isset ($property){//The method is called automatically when Isset is judged on an inaccessible property .      Echo"For inaccessible Properties {$property} Make Isset judgment <br/> "; }    function__unset ($property){//The method is automatically called when the unset operation is performed on a property that is not accessible      Echo"For inaccessible Properties {$property} for unset operation <br/> "; }  }  $t=NewTest (); Echo $t->p1. " <br/> "; Echo $t->p2. " <br/> "; //assigning values to inaccessible properties  $t-&GT;P3 = 2; //isset judgment on inaccessible properties  isset($t-p4); //unset operations on inaccessible properties  unset($t-p5); /*Run Result: 1 inaccessible properties: P2 P3 assignment to inaccessible properties P4 isset judgment on inaccessible properties P5 for UN-accessible properties Set Operation*/?>

Mates are using the __get () and __set () methods to make classes more flexible and free, which makes it easy to add properties to a class. As follows:

<?PHPHeader("Content-type:text/html;charset = Utf-8"); classtest{//defines an array for storing inaccessible properties    protected $plist=Array(); function__get ($property) {//the method is called automatically when accessing the Inaccessible property//property is inaccessible, read from plist      if(isset($this->plist[$property])) {        return $this->plist[$property]; }      Else {        returnProperties$property} not accessible "; }    }    function__set ($property,$value) {//Assigning a value to an inaccessible property automatically calls the method//the property is not accessible and is stored in the plist      $this->plist[$property] =$value; }    function__isset ($property){//The method is called automatically when Isset is judged on an inaccessible property .      $v=isset($this->plist[$property]); return $v; }    function__unset ($property){//The method is automatically called when the unset operation is performed on a property that is not accessible      unset($this->plist[$property]); }  }  $t=NewTest (); $t-&GT;P1 = 1;//Assigning a value to an inaccessible property  Echo"The value of the Inaccessible property P1 is:".$t->p1. " <br/> ";//Use the P1 property (after the previous line of code, P1 has been added to the plist)  Echo"The value of the Inaccessible property P2 is:".$t->p2. " <br/> ";//no assignment to P2//isset operation for P1 and P2 respectively  $r 1=isset($t-&GT;P1);//The result is true, but returns False if the __isset magic method is not handled  $r 2=isset($t-&GT;P2);//The result is false, and it does not exist ...  Var_dump($r 1);Echo"<br/>"; Var_dump($r 2);Echo"<br/>"; //unset operation for P1 and P2 respectively  unset($t-p1); unset($t-p2); Echo"The value of the non-existent property P1 is:".$t->p1. " <br/> "; Echo"The value of the non-existent property P2 is:".$t->p2. " <br/> "; /*Result: The value of the Unreachable property P1 is: 1 The value of the unreachable property P2 is: The property P2 is not accessible bool (TRUE) bool (false) The value of the non-accessible property P1 is: Property P1 Inaccessible Property P2 value is: property P2 Inaccessible*/?>

2. Method overloading

1) __call ()

The method is called automatically when the object's inaccessible method is called.

2) __callstatic ()

This method is called automatically when a class's inaccessible static method is called.

Examples of overloads in PHP and several common magic methods