Example of calling PHP5 magic method_PHP tutorial

PHP5 magic method

Magic function:

1. __construct()

Constructor: Called when instantiating an object,

When __construct and a constructor with a class name and a function name exist at the same time, __construct will be called and the other will not be called.

2. __destruct()

Destructor: Called when an object is deleted or the object operation terminates (the object is destroyed after the program ends).

It is always executed last.

3. __call()

Object calls a method,

If the method exists, call it directly;

If it does not exist, the __call function will be called.

4. __get()

When reading the attributes of an object, if the attribute exists, the attribute value will be returned directly; if it does not exist, the __get function will be called.

5. __set()

​When setting the properties of an object,

If the attribute exists, assign it directly;

If it does not exist, the __set function will be called.

6. __toString()

Called when printing an object. Such as echo $obj; or print $obj;

7. __clone()

Called when cloning an object. For example: $t=new Test();$t1=clone $t;

8. __sleep()

serialize was called before. If the object is relatively large and you want to delete a few things before serializing, you can consider this function.

9. __wakeup()

It is called when unserialize is used to do some object initialization work.

10. __isset()

Called when checking whether an object's properties exist. For example: isset($c->name).

11. __unset()

​Called when unsetting a property of an object. For example: unset($c->name).

12. __set_state()

​ Called when var_export is called. Use the return value of __set_state as the return value of var_export.

13. __autoload()

When instantiating an object, if the corresponding class does not exist, this method is called.

​Magic Constant

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 an include file, returns the include file name. Since PHP 4.0.2, __FILE__ always contains an absolute path, while previous versions sometimes contained a relative path.

3. __FUNCTION__

Returns the function name (new in PHP 4.3.0). Since PHP 5 this constant returns the name of the function when it was defined (case sensitive). In PHP 4 this value is always lowercase.

4. __CLASS__

Returns the name of the class (new in PHP 4.3.0). Since PHP 5 this constant returns the name of the class when it was defined (case sensitive). In PHP 4 this value is always lowercase.

5. __METHOD__

Returns the method name of the class (newly added in PHP 5.0.0). Returns the name of the method when it was defined (case-sensitive).

(1) First introduction to magic methods

Since the release of Php5.0, it has provided us with many object-oriented features, especially many easy-to-use magic methods. These magic methods allow us to simplify our coding and better design our systems. Today we will learn about the magic methods provided by php5.0.

PHP | Magic methods | __toString(),__clone(),__call(),__autoload() detailed explanation

__toString()

If I have a class:

class Person

{

private $name = “”;

private $age = 0;

function __construct($name = “”, $age = “”)

{

$this->name = $name;

$this->age = $age;

}

function say()

{

echo “name:”.$this->name.”
”.”age:”.$this->age.”
”;

}

}

Now I instantiate this class and then print this instance:

$p1 = new person(“liuzy”,20);

echo $p1; //Direct printing will cause errors

Obviously, printing the object directly will cause an error, because the object is a reference handle and cannot be printed directly. At this time, we can use the __toString() method. We add a __toString() method to the Person class:

function __toString()

{

return “I am Person,my name is “.$this->name.”
”;

}

Then refresh the page. What do you find?

Now we understand that __toString() is a method executed when printing an object directly. We can use this method to print some relevant information about the class. Note: It is two underscores, and the method must have a return value.

__clone()

We know that objects can be assigned values ​​directly, such as

$p2 = $p1; //Here is an object with two references

Then I execute:

$p1->say();

$p2->say();

Both can be executed and have the same effect.

We have another way:

$p3 = clone $p1; //Note that clone is the clone keyword. The difference here from the above is that $p3 is a new object.

At the same time, we add a method to the class:

function __clone()

{

$this->name = "I am a copy"; //Note: $this here is the object itself generated by cloning, not the current class

}

Then we execute:

$p3->say();

Print out:

name:I am a copy

age:20

At this point we understand that the __clone() method is a method executed when cloning an object. Its function is to clone the newly cloned copy

Perform attribute initialization and other operations.

__call()

The main function of this method is to execute the __call() method when an instance of this class calls a non-existent method. Note that you need to add it to the class in advance

Statement:

function __call($fname,$argus)

{

echo "The method you called: ".$fname." does not exist
";

echo "The parameter is".print_r($argus);

}

The declaration contains two parameters. The first parameter is of string type, which is the method name of the non-existent method to be called ($fname). The second parameter is

Array type is the parameter ($argus) of the non-existent method called.

__autoload()

When we usually call a class, we must first introduce the file in which the class is located (include "xxx.php"). If we call many classes on one page, then we have to use many include "xxx.php". php". Obviously this is troublesome.

The __autoload() method can help us solve this problem.

For example, we define the file where the Person class above is located as Person_class.php,

Create a new php file test.php and edit the content:

function __autoload($calssName)

{

include $className.”_class.php”; //Maybe you will understand after seeing this, right? Haha

}

$p = new Person(“mifan”, 22);

$p->say();

In this way, no errors will occur when executing the test.php page.

The __autoload() method is a method called when a class does not exist. It has a string type parameter that declares the class name of the non-existent class.

Of course, the naming of class files is also very particular. It is best to have something to do with a class, such as Person_class.php

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