Regarding the inheritance of static properties and methods on the Internet, the answers are all weird, so I just tried it directly with the code:
<code>class Base { public static $var = 'var'; public static function testStaticFun() { echo 'func'; } } class A extends Base { public function testSelf() { echo self::$var; } public function testParent() { echo parent::$var; } public function setSelf() { self::$var = 'self'; } public function setParent() { parent::$var = 'parent'; } public static function testStaticFun() { parent::testStaticFun(); echo 'over'; } } $objA = new A(); $objA->testSelf(); // var $objA->testParent(); // var $objA->setSelf(); $objA->testSelf(); // self $objA->testParent(); // self echo Base::$var; // self $objA->setParent(); $objA->testSelf(); // parent $objA->testParent(); // parent echo Base::$var; // parent Base::testStaticFun(); // func A::testStaticFun(); // func over </code>
So what exactly is static inheritance in php? Is there any difference in the behavior of static inheritance from other languages such as Java? Will the static properties and methods of the parent class be overridden? Is there only one copy of static properties after inheritance? What is the principle of inheritance implementation?
Reply content:
Regarding the inheritance of static properties and methods on the Internet, the answers are all weird, so I just tried it directly with the code:
<code>class Base { public static $var = 'var'; public static function testStaticFun() { echo 'func'; } } class A extends Base { public function testSelf() { echo self::$var; } public function testParent() { echo parent::$var; } public function setSelf() { self::$var = 'self'; } public function setParent() { parent::$var = 'parent'; } public static function testStaticFun() { parent::testStaticFun(); echo 'over'; } } $objA = new A(); $objA->testSelf(); // var $objA->testParent(); // var $objA->setSelf(); $objA->testSelf(); // self $objA->testParent(); // self echo Base::$var; // self $objA->setParent(); $objA->testSelf(); // parent $objA->testParent(); // parent echo Base::$var; // parent Base::testStaticFun(); // func A::testStaticFun(); // func over </code>
So what exactly is static inheritance in php? Is there any difference in the behavior of static inheritance from other languages such as Java? Will the static properties and methods of the parent class be overridden? Is there only one copy of static properties after inheritance? What is the principle of inheritance implementation?
Let’s break it down into several points:
1. Static members can be modified using access control keywords and can be inherited and overridden
In other words, subclasses can inherit the static variables and methods of the parent class... Follow "Keyword" Rules
2. If the subclass does not override, then the subclass actually calls the static method of the parent class
This is also very simple and clear. There is nothing to explain about the basic rules of inheritance
3. The static member holder is a class, not an object, so multiple instances of a class share the same static attribute. Modifying the static attribute in one instance will affect the static attribute in another instance
This is the key point. Understand it carefully. Single column mode also uses this feature.
So self::$var and parent::$var in the code actually point to $var in the parent class!
Finally, here is an example:
In singleton mode, $var can be understood as a database connection. After the parent class generates a connection, the inherited subclass can directly use this connection to connect to the database.
But if the subclass generates a connection $var by itself, then you need to distinguish whether it is self::$var or parent::$var when using it, because the two values may be different, and the connected databases are also different. What if it is the master and the slave. Ha ha.
happy coding~
I have answered this type of question several times here, such as this one. You will understand after reading it.
Yes, there is only one copy of static attributes!
So be careful when using static attributes to write singleton patterns.

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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