PHP magic method summary _ PHP Tutorial-php Tutorial

PHP magic method summary. 1. the _ get and _ set methods are designed for classes and their parent classes without declared attributes. _ get ($ property) access this method when an undefined property is called _ set ($ p 1. _ get, _ set

These two methods are designed for attributes that are not declared in the class and their parent class.

_ Get ($ property) access this method when an undefined property is called

_ Set ($ property, $ value) is called when an undefined attribute is assigned a value. The No declaration here includes that when an object is called, access control is proteced, private attributes (that is, attributes with no access permission)

2. _ isset and _ unset

_ Isset ($ property)

This method is called when the isset () function is called on an undefined property.

_ Unset ($ property)

When the unset () function is called on an undefined property, this method is the same as the _ get method and the _ set method. no declaration here includes when an object is called, access control is a proteced and private attribute (that is, an attribute with no access permission)

3. _ call

_ Call ($ method, $ arg_array)

When calling an undefined method is to call this access request, the undefined method here includes methods without access permission.

4. _ autoload

_ Autoload function, which is automatically called when trying to use a class that has not been defined. By calling this function, the script engine has the last chance to load the required class before a PHP error fails.

Note: The Exception thrown in the _ autoload function cannot be caught by the catch statement block and cause a fatal error.

5. _ construct and _ destruct

_ Construct constructor: This method is called when an object is created. the advantage of this method is that the constructor has a unique name, no matter what the name of its class is. in this way, you do not need to change the name of the constructor when changing the class name.

_ Destruct destructor. PHP will call this method before the object is destroyed (that is, before it is cleared from the memory). by default, PHP only releases the memory occupied by object properties and destroys object-related resources. the Destructor allows you to execute arbitrary code after using an object to clear the memory. when PHP decides that your script is no longer related to objects, the destructor will be called. in the namespace of a function, this occurs when the function returns. for global variables, this occurs 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, the variable value is NULL or unset is called.

6. _ clone

Object assignment in PHP5 is a reference assignment. if you want to copy an object, you need to use the clone method, when this method is called, the object will automatically call the _ clone magic method. if you need to perform some initialization operations in object replication, you can implement the _ clone method.

7. _ toString

The _ toString method is automatically called when an object is converted to a string. for example, if the class does not implement this method when the echo method is used to print the object, the object cannot be printed by echo. Otherwise, the following information is displayed: catchable fatal error: Object of class test cocould not be converted to string in this method must return a string before PHP 5.2.0, __tostring method only works with echo () or print (). PHP 5.2.0 and later can take effect in any string environment (for example, using the % s modifier through printf (), but cannot be used in non-string environment (for example, using the % d modifier ). From PHP 5.2.0, if an undefined _ toString method object is converted to a string, an E_RECOVERABLE_ERROR error is returned.

8. _ sleep and _ wakeup

_ SleepUsed in serialization

_ WakeupWhen deserialization is performed, call serialize () to check whether the class has the magic name_sleep function. In this case, the function will run before any serialization. It can clear the object and should return an array containing all variable names to be serialized in the object. The purpose of _ sleep is to close any database connection that an object may have, submit data in waiting or perform similar cleanup tasks. In addition, this function is useful if a very large object does not need to be fully stored. Conversely, unserialize () checks the existence of a function with the magic name _ wakeup. If yes, this function can reconstruct any resources that an object may have. _ Wakeup is used to reconstruct any database connections that may be lost during serialization and process other re-initialization tasks.

9. _ set_state

When var_export () is called, this static method is called (effective from PHP 5.1.0 ). The unique parameter of this method is an array, which contains values by array ('properties' => value ,...) Class attributes in the format.

10. _ invoke

When you try to call an object by calling a function, the __invoke method is automatically called. PHP5.3.0 and later versions are valid.

11. _ callStatic

It works in a way similar to the _ call () magic method, __callstatic () is used to handle static method calls. effective PHP versions later than PHP5.3.0 indeed enhance the _ callStatic () method definition; it must be public and declared as static. Similarly, the __call () magic method must be defined as public, and all other magic methods must be.

These two methods are designed for the class and their parent classes without declared attributes. _ get ($ property) access this method _ set ($ p...