Instructions for using php magic function_PHP tutorial

What is a magic function?
For functions starting with __, they are named magic functions. Such functions are triggered under specific conditions. For example: __set() __get(), etc.
does not exist when setting or getting Triggered when attribute.
What magic functions are there?
In general, there are the following magic functions
__construct() __destruct() __get() __set() __isset() __unset() __call () __callStatic()
__sleep() __wakeup() __toString() __set_state() __clone() __autoload()
__construct() When an object is instantiated, this method of the object is first called.
__destruct() This method is called when deleting an object or when the object operation terminates.

Copy code The code is as follows:

class test1 {
public function __construct() {
var_dump(__function__ );
}
public function __destruct() {
var_dump(__function__);
}
}
$t1 = new test1;
unset($t1);

__get is called when trying to read a property that does not exist.
__set is called when trying to write a value to a property that does not exist.
__isset is called when trying to detect a property that does not exist.
__unset is called when trying to unset a property that does not exist.

Copy code The code is as follows:

class test2 {
public $name3;
public function __set($ key, $value) {
var_dump(__function__. '
KEY:'
.$key.'
Value:'
.$value);
}
public function __get($key) {
var_dump(__function__. 'KEY:'.$key);
}
public function __isset($key) {
var_dump(__function__. 'KEY:'. $key);
}
public function __unset($key) {
var_dump(__function__. ' KEY:'.$key);
}
}
$t =new test2;
$t->name = "steven";
$t->name2;
$t->name3;
isset($t->name2);
isset($t->name3);
unset($t->name4);

__sleep is called when serializing objects
__wakeup when deserializing One thing to note when calling
on an object:
1. __sleep() must return an array or object (generally $this is returned), and the returned value will be used as the serialized
value .
If this value is not returned, serialization fails. This also means that deserialization will not trigger the __wakeup event.
2. Serialization will save the attributes assigned by default. If you want to assign the content by instantiation, you need to specify the attribute in the
of the array returned by __sleep().
For example, the difference between $id and $id2 .

Copy code The code is as follows:

class test3 {
public $name = "steven";
public $id = "1"; public $id2;
public function __sleep() {
var_dump(__function__); // Serialization was unsuccessful. No return value. Deserialization also failed //
return array("name"); // Serialization is successful. There is a return value. Deserialization is successful. The id2 attribute can be restored //
return array("name", "id2"); // Serialization is successful. There is Return value. Deserialization is successful. The id2 attribute cannot be restored
return array("name"); }
public function testEcho() {
var_dump($this->name);
var_dump ($this->id);
var_dump($this->id2);
}
public function __wakeup() {
var_dump(__function__);
$this-> ;testEcho();
}
}
$t3= new test3 ;
$t3->id2 = uniqid();
$t3s = serialize($t3);
unserialize($t3s);

__toString When printing an object directly, this method will be called

Copy code The code is as follows:

class test4 {
public function __toString() {
return "toString";
}
}
$t4 = new test4( );
echo $t4;
print $t4;
var_dump($t4);
print_r($t4);

__call($func, $param ) is called when trying to call a method that does not exist.
This method must have two parameters, the first is the name of the method to be called, and the second is a parameter array of the called method.
It should be noted that when you call a private method of a parent class in a subclass, or call a non-protected method of a class
in an instance, __call() will not be called

Copy code The code is as follows:

class test5 {
public function __call($func, $param) {
var_dump( 'Function:'.$func);
var_dump($param);
}
}
$t5 = new test5;
$t5->echoTest('xx',' xx','xx');

__callStatic() is called when trying to call a non-existent static method
This method must have two parameters, the first is the name of the called method, and the second is a parameter array of the called method .
Appears in PHP5.3

Copy code The code is as follows:

class test51 {
public function __callStatic ($fun, $param) {
var_dump('Function:'.$func);
var_dump($param);
}
}
test51::test('xx' ,'xx','xx');

__set_state() is called when an instance is exported using var_export. This method has a parameter that contains all
of the exported instance. An array of member attributes

Copy code The code is as follows:

class test6 {
public function __set_state($arr) {
var_dump($arr);
}
}
$t6 = new test6;
$t6->age = "12";
var_export($t6, true );
var_export($t6);
eval(' ​​
$b='
.var_export($t6,true).';');
print_r($b);

__clone() is called when cloning an instance.
Note:
1. In php5, assignments between objects are always passed by address reference.
2 .If you want to pass it as an actual value, you need to use the clone keyword
3. Clone is just an instance. If a member attribute in the instance is also an instance, then this member attribute will still be passed to the new instance using the reference method
.
// Assignment between objects is always passed by address reference. The age attributes of $t71 $t72 are the same.

Copy code Code As follows:

class test71 {
public $age = 10;
}
$t71 = new test71();
$t72 = $t71;
var_dump($t71->age) ;
$t71->age =12 ;
var_dump($t71->age) ;
var_dump($t72->age) ; // If you want to pass it as an actual value, you need to use the clone keyword $t73 = clone $t71; $t71->age = 13; var_dump($t71->age);
var_dump($t73-> ;age) ; // If a member property in the instance is also an instance, this member property will still be passed to the new instance by reference.

Copy code The code is as follows:

class test74 {
public $age = 10;
public $sub = null;
}
class test75 {
public $age = 11;
}
$i = new test74;
$i->sub = new test75();
$i1 =clone $i;
var_dump($i1->sub->age);
$i->sub->age = 12;
var_dump($i1->sub->age);

// Although $i and $i1 do not point to the same instance, their member attribute $sub points to the same An instance. At this time, we must use the
__clone method to copy $sub. // $i2 and $3 point to different instances. The member attribute $sub also points to different instances.

Copy code The code is as follows:

class test76 {
public $age = 10;
public $sub = null;
public function __clone() {
$this->sub = clone $this->sub;
}
}
$i2 = new test76();
$i2->sub = new test75();
$i3 = clone $i2;
$i2-> ;sub->age = 15;
var_dump($i3->sub->age);

__autoload() function. When creating an instantiation, if the corresponding If the class does not exist, it will be called

Copy code The code is as follows:

function __autoload($class) {
if ( $class == "test8" ){
require_once dirname(__FILE__).'/class8.php';
}
}
spl_autoload();
$t8 = new test8;
var_dump($t8->age);

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