Description of the PHP magic function and the Magic constants

Magic function

1. __construct ()

Called when an object is instantiated,
When __construct and a function with a class name are present, __construct is called and the other is not called.

2. __destruct ()
Called when an object is deleted or when an object operation terminates.

3. __call ()
Object calls a method,
If the method exists, it is called directly;
If it does not exist, it will call the __call function.

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

5. __set ()
When you set the properties of an object,
If the attribute exists, the value is directly assigned;
If it does not exist, the __set function is called.

6. __tostring ()
Called when an object is printed. such as Echo $obj; or print $obj;

7. __clone ()
Called when the object is cloned. such as: $t =new Test (); $t 1=clone $t;

8. __sleep ()
Serialize before being called. If the object is relatively large, want to cut a bit of the east and then serialize, you can consider this function.

9. __wakeup ()
Unserialize is called to do some initialization of the object.

10. __isset ()
Called when detecting whether an object's properties exist. such as: Isset ($c->name).

11. __unset ()
Called when a property of an object is unset. such as: unset ($c->name).

12. __set_state ()
Called when the Var_export is called. Use the return value of __set_state as the return value of Var_export.

13. __autoload ()
When an object is instantiated, the method is called if the corresponding class does not exist.

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 the include file, the include filename is returned. Since PHP 4.0.2, __file__ always contains an absolute path, and the previous version sometimes contains a relative path.

3. __function__
Returns the name of the function (PHP 4.3.0 new addition). From PHP 5 This constant returns the name (case-sensitive) when the function is defined. In PHP 4, this value is always in lowercase letters.

4. __class__
Returns the name of the class (PHP 4.3.0 new addition). From PHP 5 This constant returns the name of the class when it is defined (case-sensitive). In PHP 4, this value is always in lowercase letters.

5. __method__
Returns the method name of the class (PHP 5.0.0 new). Returns the name of the method when it is defined (case-sensitive).

(1) First knowledge of magic method
Php5.0 has provided us with a lot of object-oriented features since its release, especially for our easy-to-use magic methods that allow us to simplify our coding and better design our systems. Today we will come to know the Magic method that php5.0 offers us.