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

Reasons for PHPSession failure include configuration errors, cookie issues, and session expiration. 1. Configuration error: Check and set the correct session.save_path. 2.Cookie problem: Make sure the cookie is set correctly. 3.Session expires: Adjust session.gc_maxlifetime value to extend session time.

Methods to debug session problems in PHP include: 1. Check whether the session is started correctly; 2. Verify the delivery of the session ID; 3. Check the storage and reading of session data; 4. Check the server configuration. By outputting session ID and data, viewing session file content, etc., you can effectively diagnose and solve session-related problems.

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Configuring the session lifecycle in PHP can be achieved by setting session.gc_maxlifetime and session.cookie_lifetime. 1) session.gc_maxlifetime controls the survival time of server-side session data, 2) session.cookie_lifetime controls the life cycle of client cookies. When set to 0, the cookie expires when the browser is closed.

The main advantages of using database storage sessions include persistence, scalability, and security. 1. Persistence: Even if the server restarts, the session data can remain unchanged. 2. Scalability: Applicable to distributed systems, ensuring that session data is synchronized between multiple servers. 3. Security: The database provides encrypted storage to protect sensitive information.

Implementing custom session processing in PHP can be done by implementing the SessionHandlerInterface interface. The specific steps include: 1) Creating a class that implements SessionHandlerInterface, such as CustomSessionHandler; 2) Rewriting methods in the interface (such as open, close, read, write, destroy, gc) to define the life cycle and storage method of session data; 3) Register a custom session processor in a PHP script and start the session. This allows data to be stored in media such as MySQL and Redis to improve performance, security and scalability.

SessionID is a mechanism used in web applications to track user session status. 1. It is a randomly generated string used to maintain user's identity information during multiple interactions between the user and the server. 2. The server generates and sends it to the client through cookies or URL parameters to help identify and associate these requests in multiple requests of the user. 3. Generation usually uses random algorithms to ensure uniqueness and unpredictability. 4. In actual development, in-memory databases such as Redis can be used to store session data to improve performance and security.

Managing sessions in stateless environments such as APIs can be achieved by using JWT or cookies. 1. JWT is suitable for statelessness and scalability, but it is large in size when it comes to big data. 2.Cookies are more traditional and easy to implement, but they need to be configured with caution to ensure security.


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