看这段代码,关于PHP命名空间的用法,这里:
class TimestampBehavior extends AttributeBehavior
这里继承了AttributeBehavior这个类,但是前面命名空间并没有use yii\behaviors\AttributeBehavior;
请问如果一个类继承的类是同一个namespace中的,是否就不用use引入呢?
回复内容:
看这段代码,关于PHP命名空间的用法,这里:
class TimestampBehavior extends AttributeBehavior
这里继承了AttributeBehavior这个类,但是前面命名空间并没有use yii\behaviors\AttributeBehavior;
请问如果一个类继承的类是同一个namespace中的,是否就不用use引入呢?
这个跟命名空间没多大关系,其实是框架自动加载,能够extends类,这个类肯定要先引入
这个与 PHP 对 “命名空间解析规则”有关,请参考:名称解析规则,其中的第 3 点和第 6 点能够给你答案。
当前文件的命名空间是 yii\behaviors
,那么该文件中“非完全限定名称”的类都将会被认为是该命名空间下的类。比如这里的父类 AttributeBehavior
会被认为是 yii\behaviors\AttributeBehavior
,所以不需要使用 use
关键字显式导入该类。而不属于当前命名空间的类,使用时必须显式声明(使用 use 或者 完全限定名称),比如 yii\db\Expression
。这个与继承无关,所以要搞清楚。
对 use
关键字的理解上是有问题的,它只是声明而并不是真正的导入该类,只有当该类被使用时,才会真正引入(require)该类。yii 是有自动加载模块的,这个不需要自己关心,只要命名空间声明正确就可以了。
注:“完全限定名称”说白了就是该类的完整的命名空间+类名。

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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.

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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.

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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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