PHP的“使用"关键字和自动加载 [英] PHP's "use" Keyword and Autoloading

问题描述

我的问题分为三个部分:

My question is in three parts:

1. 放入 use 语句是立即触发自动加载器，还是等到类被使用?(延迟加载)

1. Does putting in a use statement trigger the autoloader immediately, or does it wait until the class is used? (lazy-loading)

如果自动加载不是以延迟加载的方式完成，是否会对性能产生负面影响?

If autoloading isn't done in a lazy-load fashion, could that negatively affect performance?

最好遵循哪种模式，为什么?当未使用 use 语句时，PhpStorm 将不必要的完全限定名称..."显示为代码问题.

Which pattern is best to follow, and why? PhpStorm shows "Unnecessary fully qualified name..." as a code issue when the use statement isn't employed.

以下是带有 use 语句的 Laravel 控制器的示例类定义:

Here's an example class definition for a Laravel controller with a use statement:

namespace App\Http\Controllers;

use Carbon\Carbon;

class FooController extends Controller
{
    /**
     * This action uses the Carbon class
     */
    public function bar1()
    {
        return view('foo.bar1', ['now' => new Carbon()]);
    }

    /**
     * This action does not use the Carbon class
     */
    public function bar2()
    {
        return view('foo.bar2');
    }
}

没有use语句的同一个类:

namespace App\Http\Controllers;

class FooController extends Controller
{
    /**
     * This action uses the Carbon class
     */
    public function bar1()
    {
        return view('foo.bar1', ['now' => new \Carbon\Carbon()]);
    }

    /**
     * This action does not use the Carbon class
     */
    public function bar2()
    {
        return view('foo.bar2');
    }
}

推荐答案

1) 当您执行 new Class() 语句时，该类会自动加载.

1) The class is autoloaded when you perform a new Class() statement.

2) 见 1)

3) 最好遵循哪种模式以及为什么?:

3) Which pattern is best to follow and why?:

我建议使用 use 因为你可能会遇到这样的情况:你的命名空间很长，你的代码会变得不可读.

I'd recommend to use use because you might get into a situation where you have really long namespaces and your code will become unreadable.

来自 php 文档:

此示例尝试从以下位置加载类 MyClass1 和 MyClass2分别是 MyClass1.php 和 MyClass2.php 文件.

This example attempts to load the classes MyClass1 and MyClass2 from the files MyClass1.php and MyClass2.php respectively.

<?php
spl_autoload_register(function ($class_name) {
    include $class_name . '.php';
});

$obj  = new MyClass1();
$obj2 = new MyClass2(); 
?>

命名空间只是组织类的附加功能.

Namespaces are only an additional feature to organize classes.

正如@IMSoP 在评论中指出的那样， new 并不是唯一一次触发自动加载器的时间.访问类常量，静态方法，或静态属性 也会触发它，运行 class_exists.

As @IMSoP pointed out in the comments, new is not the only time the autoloader is triggered. Accessing a class constant, static method, or static property will also trigger it, as will running class_exists.

这篇关于PHP的“使用"关键字和自动加载的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！