How to use composer

How to use composer?

Composer Usage

To use Composer, we need to first create a composer.json file in the project directory. The file describes the project's dependencies.

The file format is as follows:

{
    "require": {
        "monolog/monolog": "1.2.*"
    }
}

The above file indicates that we need to download any version of monolog starting from 1.2.

Next, just run the following command to install the dependent package:

composer install

require command

In addition to using the install command, we can also use require The command can quickly install a dependency without manually adding dependency information in composer.json:

$ composer require monolog/monolog

Composer will first find the appropriate version, then update the composer.json file, and add the monolog/monolog package in require Relevant information, then download the relevant dependencies for installation, and finally update the composer.lock file and generate the PHP automatic loading file.

update command

The update command is used to update all packages in the project, or some specified packages:

# 更新所有依赖
$ composer update
# 更新指定的包
$ composer update monolog/monolog
# 更新指定的多个包
$ composer update monolog/monolog symfony/dependency-injection
# 还可以通过通配符匹配包
$ composer update monolog/monolog symfony/*

It should be noted that, The version that a package can upgrade will be subject to version constraints, and the package will not be upgraded beyond the scope of the constrained version. For example, if the version constraint of the package in composer.json is ^1.10, and the latest version is 2.0. Then the update command cannot upgrade the package to version 2.0, but can only upgrade it to version 1.x. Please see the introduction below for version constraints.

remove command

remove command is used to remove a package and its dependencies (when the dependencies are not used by other packages), if the dependencies are used by other packages , it cannot be removed:

$ composer remove monolog/monolog
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 0 installs, 0 updates, 2 removals
  - Removing psr/log (1.0.2)
  - Removing monolog/monolog (1.23.0)
Generating autoload files
search 命令
search 命令可以搜索包：
$ composer search monolog
该命令会输出包及其描述信息，如果只想输出包名可以使用 --only-name 参数：
$ composer search --only-name monolog
show 命令
show 命令可以列出当前项目使用到包的信息：
# 列出所有已经安装的包
$ composer show
# 可以通过通配符进行筛选
$ composer show monolog/*
# 显示具体某个包的信息
$ composer show monolog/monolog

Basic constraints

Precise version

We can tell Composer the specific version installed, For example: 1.0.2, specify version 1.0.2.

Scope

Specify the scope of the package by using comparison operators. These operators include: >, >=, <, <=, !=.

You can define multiple ranges, using spaces or commas to indicate logical AND, and double vertical bars || to indicate logical OR. The priority of AND will be greater than or. Example:

>=1.0
>=1.0 <2.0
>=1.0 <1.1 || >=1.2

We can also specify a version range by using the hyphen -.

The left side of the hyphen indicates the version of >=. If the version on the right is not a complete version number, it will be completed using wildcard characters. For example, 1.0 - 2.0 is equivalent to >=1.0.0 <2.1 (2.0 is equivalent to 2.0.*), while 1.0.0 - 2.1.0 is equivalent to >=1.0.0 <=2.1.0.

Wildcard

You can use wildcard characters to set the version. 1.0.* is equivalent to >=1.0 <1.1.

Example: 1.0.*

tilde~

Let’s first explain the usage of ~ operator through the following example: ~1.2 is equivalent to >=1.2 <2.0.0, and ~1.2.3 is equivalent to >=1.2.3 <1.3.0. This version constraint method is very practical for projects that use Semantic Versioning as the version number standard.

For example ~1.2 defines the minimum minor version number, and then you can upgrade any version below 2.0 without problems, because according to the version definition of Semantic Versioning, minor version upgrades should not have compatibility question. Simply put, ~ defines the minimum version and allows the last digit of the version number to be upgraded (if you don’t understand, please look at the previous example again).

Example: ~1.2

It should be noted that if ~ acts on the major version number, such as ~1, according to the above statement, Composer can install major versions after version 1, but In fact, ~1 will be treated as ~1.0, and only minor versions can be added, not major versions.

The accent ^

^ operator behavior is closely related to Semantic Versioning, which allows upgrading the version to a secure version. For example, ^1.2.3 is equivalent to >=1.2.3 <2.0.0, because there should be no compatibility issues with versions before version 2.0. For versions before 1.0, this constraint method also takes security issues into consideration. For example, ^0.3 will be treated as >=0.3.0 <0.4.0.

Example: ^1.2.3

For more composer technical articles, please visit the composer command usage graphic tutorial column!

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