


Application Analysis of PHP Static Calling of Non-static Methods_PHP Tutorial
Calling non-static methods statically! ! This is unimaginable in java and c#, and it is absolutely impossible. Such errors will be pointed out at the compilation stage in these languages. But what about dynamic languages like php? First of all, there is no syntax error in this. php -l cannot find the error. What if it runs?
Look at an example first
class myClass
{
private $name = "myClass";
public function echoName(){
echo $this->name;
}
public function getName(){
echoName();
}
}
class newClass
{
private $name = "newClass" ;
public function echoName(){
echo $this->name;
}
public function test() {
myClass::getName();
echo "n";
}
}
$app = new newClass();
$app->test();
What is the final call result of this code? (Running environment PHP 5.3.10)
Looking at this result, there are several things worth noting:
The first is myClass::getName(), which is a static function call
But look at the getName() function of myClass, it is not a static function.
Secondly return the structure
First return PHP Strict Standards Error. People who are familiar with PHP should know that Strict Error is PHP's coding standardization warning, which is generally an error reported by PHP in order to maintain forward compatibility. That said, static calling of non-static functions is allowed in a version before php5.3, but it is not recommended in later versions! !
Okay, if you comment out Strict Error in error_reporting now, the return result will become newClass!!
In the php4 version, the subclass needs to call the method of the parent class, but the subclass has a method with the same name, so $this cannot be used, so php4 provides a method like (parentClassName::method()). (Of course php5 adds the keyword parent)
But this method provided by php4 actually allows static calling of a non-static method! ! Due to the need for forward compatibility in the background, this feature has become a feature that cannot be deleted (it must be ensured that the code of the previous version can run in the PHP environment of the later version).
Just added Strict Error to prompt this kind of call.
Underlying implementation reasons
Okay, as for the implementation reasons why this situation occurs, this article by Brother Niao has an explanation http://www.laruence.com/2012/06/ 14/2628.html
First of all, you need to subvert your own point of view. What is a static call? It does not mean that there is:: it is a static call, but look at the calling scope.
“The object pointed to by the $this pointer is the calling scope when this method is called.”
I will change the sentence translation:
Static calls do not have calling scope. The object pointed to by $this in non-static calls $this->abc() is the calling scope.
Calling scope is passed when each sentence is called.
Understand the following code:
class A {
public function __construct() {
}
}
class B extends A {
public function __construct() {
parent::__construct();
}
}
The parent::_construct() here is the calling scope of the subclass that converts it into the calling scope of the parent class A. This is not a static call.
Back to the top example
myClass::getName();
At this time, since keywords like parent are not used and $this is not reassigned, the calling scope has not changed and is still $app. That is to say, at this time, all $this pointers that appear point to $app.
Okay, the following things are easy to understand. echo $this->name; naturally calls the name attribute of the calling scope.

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.

In PHP, you can effectively prevent CSRF attacks by using unpredictable tokens. Specific methods include: 1. Generate and embed CSRF tokens in the form; 2. Verify the validity of the token when processing the request.
