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Summary of common magic methods in PHP_PHP tutorial
- WBOYOriginal
- 2016-07-13 17:50:36819browse
Commonly used magic methods are: __Tostring () __Call() __autoLoad() __ clone() __GET() __SET() __isset() __unset()
1.__Tostring() is used to call when defining an output object reference. It is often used to print information about some objects. There must be a return value
eg: There is a person class
Persion per =new persion()
Echo per; //Direct calling will cause an error
We can add the __tostring() method
in the class definition
Function __Tostring()
{
$str=this->$name.this->age;
Return $str;
}
2. Copying of __clone() objects
Reference assignment
$per1=$per2; And this has only one address in memory
And $per1=clone $per2 There are two memory addresses at this time
3.__call() method is automatically executed when calling a function that does not exist in the class instance
If you try to call a function that does not exist in the class, a syntax error will occur. In order to provide a friendly prompt
We can declare the Call() method in the class;
Function __call($funName,$argu)
{
Echo "The function named ".$funName." with parameter ".printf($argh)." does not exist",
}
4.__autoLoad automatically loads the class files used. This function adds
to the referenced page.
We have all used this situation. When we need to call other php files in the page, we need to use the include method
But if there are dozens of pages that need to be referenced, it would be too cumbersome. We can use the autoload method on the page
Function __autoload($className)
{
Include $className.".php";
}
In this way, wherever other classes are referenced, the class file will be automatically referenced. The name of the prerequisite class file must be class name.php
5.__GET() Access private properties in the class
If a property in a class is set as a private property, it cannot be accessed in an instance of the class, but how can it be accessed?
We can use __GET()
Eg:
There are
in the category
Class person
{
Private $name;
Private $age;
}
Instantiate person per=new person()
Per->$name; //The value cannot be obtained in this way
But if we add the __GET method to the class
Function __GET($proName)
{
Return this->$proName;
}
We can access it by calling Per->$name again
Some people may raise questions by doing this. In this way, private variables can be accessed directly. What is the difference between declaring them public?
If it is declared public, we can read it arbitrarily. If it is private, if we add a get method, then the content of the GET method will be called every time the private attribute is called, so we can add some logical processing to the get method.
6.__SET() sets private attributes in the class www.2cto.com
The principle is the same as above. We can add the __SET() function to the class. Whenever a private attribute is assigned a value by calling a class instance, the __SET function will be executed. Function prototype:
Function __SET($proName,$value)
{
This->$proName=$value;
}
Since it is method assignment, we can do some logical processing
7.__isset() is automatically called when determining whether private attributes or methods in the class exist
First, let’s introduce the isset method. This method is used to determine whether properties and methods exist. However, we cannot determine whether a private property in a class exists through a class instance
If we use isset(per->$name);//The return value is false, but the $name attribute does exist, how to solve it?
Solution:
1. Define $name as a private attribute
2.
Add
in class definition
Function __isset($proName)
{
Return isset(this->$proName);//Private properties can be accessed inside the class
}
In this case, we call isset($name) again; the return value will be true;
8.__unset() is automatically called when clearing private variables in a class
Combined with it is unset(). The unset method can delete attributes. When we need to delete attributes in a class, if it is a public attribute, we can directly
Delete, but if it is private, we cannot achieve it through this method only
How to implement it? We can use the __unset() method to achieve this function. We need to add
to the class.
Function __unset($proName)
{
Unset(this->$proName);
}
Now we call unset($name); to delete the private attribute $name in the person class
Excerpted from jt521xlg’s column