5 Composer tips that PHP developers should know, developer composer_PHP tutorial

5 Composer tips that PHP developers should know, developer composer

Composer is a new generation of PHP dependency management tool. For its introduction and basic usage, you can read this article "A New Era of Composer PHP Dependency Management". This article introduces five tips for using Composer, hoping to bring convenience to your PHP development.

1. Only update a single library

You only want to update a specific library and don’t want to update all its dependencies. It’s very simple:

composer update foo/bar 

In addition, this trick can also be used to solve the "warning message problem". You must have seen warning messages like this:

<code>Warning: The lock file is not up to date with the latest changes in composer.json, you may be getting outdated dependencies, run update to update them. 
</code>

Damn, what went wrong? Don't panic! If you edit composer.json, you should see a message like this. For example, if you add or update details such as a library description, author, more parameters, or even just a space, it will change the md5sum of the file. Then Composer will warn you that the hash value is different from the one recorded in composer.lock.

So what should we do? The update command can update the lock file, but if you only add some descriptions, it should not update any libraries. In this case, just update nothing:

$ composer update nothing
Loading composer repositories with package information 
Updating dependencies 
Nothing to install or update 
Writing lock file 
Generating autoload files 

This way, Composer will not update the library, but it will update composer.lock. Note that nothing is not a keyword of the update command. There is just no nothing result caused by this package. If you type foobar, the result will be the same.

If the Composer version you are using is new enough, you can use the --lock option directly:

composer update --lock 

2. Install the library without editing composer.json

You may find it too troublesome to modify composer.json every time you install a library, then you can use the require command directly.

composer require "foo/bar:1.0.0" 

This method can also be used to quickly open a new project. The init command has the --require option, which can automatically write composer.json: (note that we use -n so that we don’t have to answer the question)

$ composer init --require=foo/bar:1.0.0 -n
$ cat composer.json
{
  "require": {
    "foo/bar": "1.0.0"
  }
}

3. Derivation is easy

Have you tried the create-project command during initialization?

composer create-project doctrine/orm path 2.2.0 

This will automatically clone the repository and check out the specified version. This command is very convenient to use when cloning a library, as there is no need to search for the original URI.

4. Consider caching, distpacket priority

Composer from the past year will automatically archive the dist packages you downloaded. By default, the dist package is used for tagged versions, such as "symfony/symfony": "v2.1.4", or wildcards or version ranges, "2.1.*" or ">=2.2,3f8d538d070f67382a3eedb21e5da245=2.2,<2.3-dev"（如果你使用stable作为你的minimum-stability）。

dist包也可以用于诸如dev-master之类的分支，Github允许你下载某个git引用的压缩包。为了强制使用压缩包，而不是克隆源代码，你可以使用install和update的--prefer-dist选项。

下面是一个例子（我使用了--profile选项来显示执行时间）：

$ composer init --require="twig/twig:1.*" -n --profile
Memory usage: 3.94MB (peak: 4.08MB), time: 0s

$ composer install --profile
Loading composer repositories with package information 
Installing dependencies 
 - Installing twig/twig (v1.12.2)
  Downloading: 100%

Writing lock file 
Generating autoload files 
Memory usage: 10.13MB (peak: 12.65MB), time: 4.71s

$ rm -rf vendor

$ composer install --profile
Loading composer repositories with package information 
Installing dependencies from lock file 
 - Installing twig/twig (v1.12.2)
  Loading from cache

Generating autoload files 
Memory usage: 4.96MB (peak: 5.57MB), time: 0.45s 

这里，twig/twig:1.12.2的压缩包被保存在~/.composer/cache/files/twig/twig/1.12.2.0-v1.12.2.zip。重新安装包时直接使用。

5. 若要修改，源代码优先

当你需要修改库的时候，克隆源代码就比下载包方便了。你可以使用--prefer-source来强制选择克隆源代码。

composer update symfony/yaml --prefer-source 

接下来你可以修改文件：

composer status -v 
You have changes in the following dependencies: 
/path/to/app/vendor/symfony/yaml/Symfony/Component/Yaml:
  M Dumper.php

当你试图更新一个修改过的库的时候，Composer会提醒你，询问是否放弃修改：

$ composer update
Loading composer repositories with package information 
Updating dependencies 
 - Updating symfony/symfony v2.2.0 (v2.2.0- => v2.2.0)
  The package has modified files:
  M Dumper.php
  Discard changes [y,n,v,s,?]?

为生产环境作准备

最后提醒一下，在部署代码到生产环境的时候，别忘了优化一下自动加载：

composer dump-autoload --optimize 

安装包的时候可以同样使用--optimize-autoloader。不加这一选项，你可能会发现20%到25%的性能损失。

如果你需要帮助，或者想要了解某个命令的细节，你可以阅读官方文档或者中文文档，也可以查看JoliCode做的这个交互式备忘单。

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原文地址：5 features to know about Composer PHP
译文地址：PHP 开发者该知道的 5 个 Composer 小技巧

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