What are the magic methods of php class

The magic methods of the PHP class are: 1. "__sleep" method, which returns an array containing the names of all variables in the object that should be serialized; 2. "__wakeup" method, which is the opposite of "__sleep"; 3. , "__tostring" method, returns the content to be output when a class is treated as a string, etc.

The operating environment of this tutorial: Windows 7 system, PHP version 5.6. This method is suitable for all brands of computers.

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Magic method of PHP class

PHP will all start with a double underscore (__ ) are reserved as magic methods, so except for the following magic methods when defining class methods, it is recommended not to start with __.

__sleep: Returns an array containing the names of all variables in the object that should be serialized. When the serialize function serializes a class, it first checks whether the __sleep method exists in the class. If present, this method is called before serialization. And only the properties in the array returned by __sleep are serialized. If __sleep returns nothing, null will be serialized and an E_NOTICE level error will be generated. __sleep cannot return private members of the parent class, otherwise an E_NOTICE level error will occur. This method is useful for objects that are large but don't need to hold all the data.

__wakeup: Contrary to __sleep, when the unserialize function is deserializing, it will first check whether the __wakeup method exists in the class. If it exists, the method will be called first and then the deserialization operation will be performed. Used to prepare resources required by some objects before deserialization, or other initialization operations.

__tostring: Returns the content to be output when a class is treated as a string. This method must return a string and cannot throw an exception in this method, otherwise a fatal error will occur. Before PHP5.2, this method only took effect when echo and print were used directly. After that, it can take effect in any string environment. If an object that does not define the __toString method is converted to a string, a fatal error will occur.

__invoke: Starting from PHP 5.3, this method will be called when trying to call an object as a function.

__set_state: Starting from PHP5.1, this static method will be called when the var_export function is called to export a class. This method has only one parameter, which is an array containing attributes as keys and attribute values ​​as values. This method can be used to control which members can be exported.

__debugInfo: Starting from PHP5.6, this method will be called when the var_dump function is called to print the attributes of the object. This method can be used to control which attributes can be printed. If this method is not defined, all the attributes in the object will be printed. Public, protected, and private attributes will all be printed. Returns an array containing properties that can be printed.

__construct: Constructor.

__destruct: destructor.

__set, __get, __isset, __unset: overloaded attributes.

__call, __callstatic: overloaded methods.

__clone: ​​Object copy.

<?php
class A{
    private $var;
    public $var2="b";
    
    function __construct(){
        $this->var=mt_rand();
    }
    
    function __sleep(){
        return array("var","var2");
    }
    
    function __wakeup(){
        $this->var=mt_rand();
    }
    
    function __toString(){
        return "class[".__CLASS__."]:{var:$this->var,var2:$this->var2}\n";
    }
    
    function __invoke($arg){
        $this->var2=$arg;
    }
    
    static function __set_state($arr){
        $a=new A();
        $a->var=$arr[&#39;var&#39;];
        return $a;
    }
}
$a=new A();
$str=serialize($a);
echo "$str\n";
$b=unserialize($str);
var_dump($b);
$b("inv-b");
echo $b;
eval(&#39;$c=&#39; . var_export($b,true) . &#39;;&#39;);
var_dump($c);
?>

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