Introduction to PHP's magic functions and magic constants_PHP Tutorial

Magic function

1. __construct()

Called when instantiating an object. When __construct and a function with the class name and function name exist at the same time, __construct will be called and the other will not be called.

2. __destruct()

Called when an object is deleted or the object operation terminates.

3. __call()

The object calls a method, If the method exists, call it directly; If it does not exist, the __call function will be called.

4. __get()

When reading the properties of an object, If the attribute exists, the attribute value is returned directly; If it does not exist, the __get function will be called.

5. __set()

When setting the properties of an object, If the attribute exists, assign it directly; If it does not exist, the __set function will be called.

6. __toString()

Called when printing an object. Such as echo $obj; or print $obj;

7. __clone()

Called when cloning an object. For example: $t=new Test();$t1=clone $t;

8. __sleep()

serialize was called before. If the object is relatively large and you want to delete a little bit before serializing it, you can consider this function.

9. __wakeup()

Called when unserialize is used to do some object initialization work.

10. __isset()

Called when checking whether a property of an object exists. Such as: isset($c->name).

11. __unset()

Called when unsetting a property of an object. For example: unset($c->name).

12. __set_state()

Called when var_export is called. Use the return value of __set_state as the return value of var_export.

13. __autoload()

When instantiating an object, if the corresponding class does not exist, this method is called.

Magic Constants

1. __LINE__

Returns the current line number in the file.

2. __FILE__

Returns the full path and file name of the file. If used in an include file, returns the include file name. As of PHP 4.0.2, __FILE__ always contains an absolute path, while versions before that sometimes contained a relative path.

3. __FUNCTION__

Return function name (new in PHP 4.3.0). Since PHP 5 this constant returns the name of the function as it was defined (case sensitive). In PHP 4 this value is always lowercase.

4. __CLASS__

Returns the name of the class (new in PHP 4.3.0). Since PHP 5 this constant returns the name of the class when it was defined (case sensitive). In PHP 4 this value is always lowercase.

5. __METHOD__

Returns the method name of the class (newly added in PHP 5.0.0). Returns the name of the method as it was defined (case-sensitive).

First introduction to magic methods

Php5.0 has provided us with many object-oriented features since its release, especially many easy-to-use magic methods that allow us to simplify our coding and better design our systems. Today we will learn about the magic methods provided by php5.0.

__get() is called when trying to read a property that does not exist.

If you try to read a property that does not exist in an object, PHP will give an error message. If we add the __get method to the class, we can use this function to implement various operations similar to reflection in Java.

class Test
{
public function __get($key)
{
  echo $key . " 不存在";
}
}
$t = new Test();
echo $t->name;

will output: name does not exist

__set() is called when trying to write a value to a property that does not exist.

class Test
{
public function __set($key,$value)
{
  echo '对'.$key . "附值".$value;
}
}
$t = new Test();
$t->name = "aninggo";

will output: Attach value to name aninggo

__call() This method is called when trying to call a method that does not exist on the object.

class Test
{
public function __call($Key, $Args)
{
  echo "您要调用的 {$Key} 方法不存在。你传入的参数是：" . print_r($Args, true);
}
}
$t = new Test();
$t->getName(aning,go);

The program will output: The getName method you are trying to call does not exist.

The parameters are:

Array
(
[0] => aning
[1] => go
)

__toString() is called when printing an object

This method is similar to java's toString method. This function is called back when we print the object directly

class Test
{
public function __toString()
{
  return "打印 Test";
}
}
$t = new Test();
echo $t;

When running echo $t;, $t->__toString(); will be called to output : Print Test

__clone() is called when the object is cloned

class Test
{
public function __clone()
{
  echo "我被复制了！";
}
}
$t = new Test();
$t1 = clone $t;

Program output: I was copied

http://www.bkjia.com/PHPjc/752480.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/752480.htmlTechArticleThe magic function __construct() is called when instantiating an object. When __construct is combined with the class name and the function name When functions exist at the same time, __construct will be called and the other will not. __destr...