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Summary of PHP magic methods_PHP tutorial
- WBOYOriginal
- 2016-07-13 10:31:381008browse
Summary of magic methods in PHP: __construct, __destruct, __call, __callStatic,__get, __set, __isset, __unset, __sleep, __wakeup, __toString, __set_state, __clone and __autoload
1. __get, __set
These two methods are designed for properties that are not declared in the class and their parent class
__get( $property ) Access this method when calling an undefined property
__set( $property, $value ) is called when assigning a value to an undefined property
The non-declarations here include attributes whose access control is protected and private (i.e. attributes without permission to access) when called using objects
2. __isset, __unset
__isset( $property ) This method is called when the isset() function is called on an undefined property
__unset( $property ) This method is called when the unset() function is called on an undefined property
Same as the __get method and __set method, the undeclared here includes attributes whose access control is protected and private (that is, attributes without permission to access) when called using an object
3. __call
__call( $method, $arg_array ) This call is called when calling an undefined method
The undefined methods here include methods that do not have permission to access
4. __autoload
__autoload function, which is automatically called when trying to use a class that has not been defined yet. By calling this function, the scripting engine has a last chance to load the required classes before PHP fails with an error.
Note: Exceptions thrown in the __autoload function cannot be caught by the catch statement block and result in a fatal error. 5. __construct, __destruct
__construct constructor, this method is called when an object is created. The advantage of using this method is that the constructor can have a unique name, no matter what the name of the class it is in. In this way, you are changing the name of the class , there is no need to change the name of the constructor
__destruct destructor method, PHP will call this method before the object is destroyed (that is, before it is cleared from memory)
By default, PHP only releases the memory occupied by object properties and destroys object-related resources.
Destructors allow you to execute arbitrary code to clear memory after using an object.
When PHP decides that your script is no longer associated with the object, the destructor will be called.
Within the namespace of a function, this will happen when the function returns.
For global variables, this happens at the end of the script. If you want to explicitly destroy an object, you can assign any other value to the variable pointing to the object. Usually assign the variable to NULL or call unset.
6. __clone
Object assignment in PHP5 uses reference assignment. If you want to copy an object, you need to use the clone method. When calling this method, the object will automatically call the __clone magic method
If you need to perform some initialization operations during object copying, you can implement it in the __clone method
7.__toString
The __toString method is automatically called when converting an object into a string, such as when using echo to print an object
If the class does not implement this method, the object cannot be printed through echo, otherwise it will display: Catchable fatal error: Object of class test could not be converted to string in
This method must return a string. Before PHP 5.2.0, the __toString method can only take effect when used in conjunction with echo() or print(). After PHP 5.2.0, it can be used in any string environment (for example, through printf(), using the %s modifier), but cannot be used in non-string environments (such as using the %d modifier). From PHP 5.2.0, if an object that does not define the __toString method is converted to a string, an E_RECOVERABLE_ERROR error will be reported.
8. __sleep, __wakeup
__sleep is used when serializing
__wakeup is called during deserialization
serialize() checks whether there is a function with the magic name __sleep in the class. If so, the function will run before any serialization. It clears the object and should return an array containing the names of all variables in the object that should be serialized.
The purpose of using __sleep is to close any database connections the object may have, submit pending data, or perform similar cleanup tasks. Additionally, this function is useful if you have very large objects that do not need to be stored completely.
In contrast, unserialize() checks for the existence of a function with the magic name __wakeup. This function can reconstruct any resources the object may have, if present.
The purpose of using __wakeup is to re-establish any database connections that may have been lost during serialization and to handle other re-initialization tasks.
9. __set_state
This static method will be called when var_export() is called (valid since PHP 5.1.0).
The only parameter of this method is an array, which contains class properties arranged in the format of array('property' => value, ...).
10. __invoke
When trying to call an object by calling a function, the __invoke method is automatically called.
PHP5.3.0 or above is valid
11. __callStatic
It works similar to the __call() magic method, __callStatic() is to handle static method calls,
PHP5.3.0 or above is valid
PHP does tighten the definition of the __callStatic() method; it must be public and must be declared static. Likewise, the __call() magic method must be defined as public, as must all other magic methods.