PHP Magic Methods And Magic Constants 2023

1. Class method:
2. Method overloading:
3. Attribute overloading:
4. Serialization related: 
5. Manipulating classes and object methods:
6. Constant:

Class method:

1. __construct();

Description: A class with a constructor will call this method every time a new object is created, which is suitable for doing some initialization work before using the object. If a constructor is defined in a subclass, the constructor of its parent class will not be called implicitly. To execute the constructor of the parent class, you need to call parent::__construct() in the constructor of the child class. If the subclass does not define a constructor, it will be inherited from the parent class just like a normal class method.

2. __destruct();

Description: A destructor is executed when all references to an object are deleted or when the object is explicitly destroyed. 

Method overloading:

3. __call(); Description: When calling an inaccessible method in an object, the __call(); method will be called.
4. __callStatic(); Description: When calling an inaccessible method in a static way, the __callStatic(); method will be called.

Attribute overloading:

( only valid for private protected member attributes in the class )

5. __get(); Attribute overloading: ( only valid for private protected member attributes in the class )when reading the value of an inaccessible attribute . Description: __get() is called
6. __set();when assigning a value to an inaccessible attribute . Description: __set() will be called
7. __isset();is called on an inaccessible attribute isset() or empty() is called when Description: __isset() .
8. __unset();is called on an inaccessible attribute unset() is called when Description: __unset() .

Serialization related: 

9. __sleep() ; Description: Called during serialization, the serialize() function will check whether the magic method exists in the class. If present, this method will be called before performing the serialization operation.
10. __wakeup(); Description: unserialize() checks for the existence of a __wakeup() method. If it exists, this method will be called first and used in deserialization operations, such as re-establishing a database connection, or performing other initialization operations.

Manipulating classes and object methods:

11. __toString(); Description: The method is used to call when a class is treated as a string, such as outputting a class as a string
12. __invoke(); when attempting to invoke an object as a function . Description: The __invoke() method is automatically invoked
13. __ set_state(); Description: This static method is called when calling var_export() to export a class. The only parameter of this method is an array
14. __clone(); Description: When the copy is completed, if the __clone() method is defined, the __clone() method in the newly created object (the object generated by copying ) will be called, which can be used to modify the value of the attribute.
15. __autoload(); Description: This method can automatically instantiate the required classes. When the program wants to use a class but has not been instantiated, the method looks for a file with the same name as the class in the specified path. Otherwise report an error.
16 __debugInfo(); Description : The feature added in php5.6, var_dump() is triggered when a class is created, and returns an array containing object properties.

Explanation: PHP reserves all class methods starting with __ (two underscores) as magic methods. So when defining class methods, except for the magic methods mentioned above, it is recommended not to prefix them with __. You cannot use these method names when naming your own class methods, unless you want to use their magic functions.

Constant:

__LINK__ // The current line number in the file.
__FILE__ //The full path and filename of the file. If used in an included file, returns the name of the included file.
__DIR__ //The directory where the file is located. If used in an included file, returns the directory where the included file resides, equivalent to dirname(__FILE__).
__FUNCTION__ //Function name. Since PHP 5 this constant returns the name (case sensitive) of the function as it was defined. In PHP 4 the value is always lowercase.
__CLASS__ //The name of the class. Since PHP 5 this constant returns the name (case sensitive) of the class as it was defined. In PHP 4 the value is always lowercase.
__METHOD__ //The method name of the class (newly added in PHP 5.0.0). Returns the name (case-sensitive) of the method as it was defined.
__NAMESPACE__ //The name of the current namespace (case sensitive). This constant is defined at compile time (new in PHP 5.3.0).

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