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Summary of PHP magic methods_PHP tutorial
- WBOYOriginal
- 2016-07-20 11:12:54719browse
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 attribute. The undeclared here includes attributes whose access control is protected and private (that is, attributes without permission to access) when called using an object.
2, __isset, __unset
__isset( $property )
This method is called when the isset() function is called on an undefined property
__unset( $property )
When calling the unset() function on an undefined attribute, calling this method is the same as the __get method and __set method. The undeclared here includes attributes whose access control is protected and private when called using an object ( That is, attributes that do not have permission to access)
3. __call
__call( $method, $arg_array )
When calling an undefined method, this access request is called. 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 the object's attributes and destroys the resources related to the object. The destructor allows You execute arbitrary code to clear memory after using an object. When PHP decides that your script is no longer relevant to the object, the destructor will be called. Within a function's namespace, this will happen on function return. 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. Typically 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 when copying the object, you can Implemented in __clone method
7.__toString
__toString method is automatically called when converting an object into a string. For example, 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. Prior to PHP 5.2.0, the __toString method only took effect when used in conjunction with echo() or print(). After PHP 5.2.0, it can take effect 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 Use
when serializing__wakeup Call serialize() during deserialization to check 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. In addition, this function is also useful if you have very large objects that do not need to be stored completely. Conversely, 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 reestablish any database connections that may have been lost during serialization and to handle other reinitialization 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 containing 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. Valid for PHP5.3.0 or above
11. __callStatic
It works similar to the __call() magic method, __callStatic() is to handle static method calls, valid in PHP5.3.0 and above. PHP has indeed strengthened 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.