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# Basic usage
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-## Installing
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+## Introduction
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-If you have not yet installed Composer, refer to the [Intro](00-intro.md) chapter.
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+If you have not yet installed Composer, refer to the [Intro](00-intro.md)
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+chapter. For our basic usage introduction, we will be installing
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+`monolog/monolog`, a logging library. Note that for the sake of simplicity,
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+this introduction will assume you have performed a [local](00-intro.md#locally)
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+install of Composer.
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## `composer.json`: Project Setup
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@@ -10,9 +14,6 @@ To start using Composer in your project, all you need is a `composer.json`
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file. This file describes the dependencies of your project and may contain
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other metadata as well.
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-The [JSON format](http://json.org/) is quite easy to write. It allows you to
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-define nested structures.
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-
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### The `require` Key
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The first (and often only) thing you specify in `composer.json` is the
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@@ -27,15 +28,15 @@ depends on.
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}
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```
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-As you can see, `require` takes an object that maps **package names** (e.g. `monolog/monolog`)
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-to **package versions** (e.g. `1.0.*`).
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+As you can see, `require` takes an object that maps **package names**
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+(e.g. `monolog/monolog`) to **version constraints** (e.g. `1.0.*`).
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### Package Names
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The package name consists of a vendor name and the project's name. Often these
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-will be identical - the vendor name just exists to prevent naming clashes. It allows
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-two different people to create a library named `json`, which would then just be
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-named `igorw/json` and `seldaek/json`.
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+will be identical - the vendor name just exists to prevent naming clashes. It
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+allows two different people to create a library named `json`, which would then
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+just be named `igorw/json` and `seldaek/json`.
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Here we are requiring `monolog/monolog`, so the vendor name is the same as the
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project's name. For projects with a unique name this is recommended. It also
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@@ -45,53 +46,20 @@ smaller decoupled parts.
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### Package Versions
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-In the previous example we were requiring version [`1.0.*`](http://semver.mwl.be/#?package=monolog%2Fmonolog&version=1.0.*) of monolog. This
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-means any version in the `1.0` development branch. It would match `1.0.0`,
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-`1.0.2` or `1.0.20`.
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-
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-Version constraints can be specified in a few different ways.
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-
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-Name | Example | Description
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--------------- | ------------------------------------------------------------------------ | -----------
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-Exact version | `1.0.2` | You can specify the exact version of a package.
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-Range | `>=1.0` `>=1.0 <2.0` <code>>=1.0 <1.1 || >=1.2</code> | By using comparison operators you can specify ranges of valid versions. Valid operators are `>`, `>=`, `<`, `<=`, `!=`. <br />You can define multiple ranges. Ranges separated by a space (<code> </code>) or comma (`,`) will be treated as a **logical AND**. A double pipe (<code>||</code>) will be treated as a **logical OR**. AND has higher precedence than OR.
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-Hyphen Range | `1.0 - 2.0` | Inclusive set of versions. Partial versions on the right include are completed with a wildcard. For example `1.0 - 2.0` is equivalent to `>=1.0.0 <2.1` as the `2.0` becomes `2.0.*`. On the other hand `1.0.0 - 2.1.0` is equivalent to `>=1.0.0 <=2.1.0`.
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-Wildcard | `1.0.*` | You can specify a pattern with a `*` wildcard. `1.0.*` is the equivalent of `>=1.0 <1.1`.
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-Tilde Operator | `~1.2` | Very useful for projects that follow semantic versioning. `~1.2` is equivalent to `>=1.2 <2.0`. For more details, read the next section below.
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-Caret Operator | `^1.2.3` | Very useful for projects that follow semantic versioning. `^1.2.3` is equivalent to `>=1.2.3 <2.0`. For more details, read the next section below.
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-
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-### Next Significant Release (Tilde and Caret Operators)
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-
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-The `~` operator is best explained by example: `~1.2` is equivalent to
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-`>=1.2 <2.0.0`, while `~1.2.3` is equivalent to `>=1.2.3 <1.3.0`. As you can see
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-it is mostly useful for projects respecting [semantic
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-versioning](http://semver.org/). A common usage would be to mark the minimum
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-minor version you depend on, like `~1.2` (which allows anything up to, but not
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-including, 2.0). Since in theory there should be no backwards compatibility
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-breaks until 2.0, that works well. Another way of looking at it is that using
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-`~` specifies a minimum version, but allows the last digit specified to go up.
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-
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-The `^` operator behaves very similarly but it sticks closer to semantic
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-versioning, and will always allow non-breaking updates. For example `^1.2.3`
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-is equivalent to `>=1.2.3 <2.0.0` as none of the releases until 2.0 should
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-break backwards compatibility. For pre-1.0 versions it also acts with safety
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-in mind and treats `^0.3` as `>=0.3.0 <0.4.0`
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-
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-> **Note:** Though `2.0-beta.1` is strictly before `2.0`, a version constraint
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-> like `~1.2` would not install it. As said above `~1.2` only means the `.2`
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-> can change but the `1.` part is fixed.
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-
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-> **Note:** The `~` operator has an exception on its behavior for the major
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-> release number. This means for example that `~1` is the same as `~1.0` as
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-> it will not allow the major number to increase trying to keep backwards
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-> compatibility.
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+In the previous example we were requiring version
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+[`1.0.*`](http://semver.mwl.be/#?package=monolog%2Fmonolog&version=1.0.*) of
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+monolog. This means any version in the `1.0` development branch. It is the
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+equivalent of saying versions that match `>=1.0 <1.1`.
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+
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+Version constraints can be specified in several ways, read
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+[versions](articles/versions.md) for more in-depth information on this topic.
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### Stability
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-By default only stable releases are taken into consideration. If you would like
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-to also get RC, beta, alpha or dev versions of your dependencies you can do
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-so using [stability flags](04-schema.md#package-links). To change that for all
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-packages instead of doing per dependency you can also use the
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+By default only stable releases are taken into consideration. If you would
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+like to also get RC, beta, alpha or dev versions of your dependencies you can
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+do so using [stability flags](04-schema.md#package-links). To change that for
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+all packages instead of doing per dependency you can also use the
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[minimum-stability](04-schema.md#minimum-stability) setting.
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If you are using range comparisons when selecting non-stable packages, and you
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@@ -119,15 +87,15 @@ the `minimum-stability` setting and each package's stability flags.
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### Test version constraints
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-You can test version constraints using [semver.mwl.be](http://semver.mwl.be). Fill in
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-a package name and it will autofill the default version constraint which Composer would add
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-to your `composer.json` file. You can adjust the version constraint and the tool will highlight
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-all releases that match.
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+You can test version constraints using [semver.mwl.be](http://semver.mwl.be).
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+Fill in a package name and it will autofill the default version constraint
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+which Composer would add to your `composer.json` file. You can adjust the
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+version constraint and the tool will highlight all releases that match.
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## Installing Dependencies
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-To fetch the defined dependencies into your local project, just run the
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-`install` command of `composer.phar`.
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+To install the defined dependencies for your project, just run the
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+`install` command.
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```sh
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php composer.phar install
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@@ -139,11 +107,10 @@ It's a convention to put third party code into a directory named `vendor`.
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In case of monolog it will put it into `vendor/monolog/monolog`.
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> **Tip:** If you are using git for your project, you probably want to add
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-> `vendor` into your `.gitignore`. You really don't want to add all of that
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+> `vendor` in your `.gitignore`. You really don't want to add all of that
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> code to your repository.
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-Another thing that the `install` command does is it adds a `composer.lock`
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-file into your project root.
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+You will notice the `install` command also created a `composer.lock` file.
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## `composer.lock` - The Lock File
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@@ -151,72 +118,72 @@ After installing the dependencies, Composer writes the list of the exact
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versions it installed into a `composer.lock` file. This locks the project
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to those specific versions.
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-**Commit your application's `composer.lock` (along with `composer.json`) into version control.**
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+**Commit your application's `composer.lock` (along with `composer.json`)
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+into version control.**
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-This is important because the `install` command checks if a lock file is present,
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-and if it is, it downloads the versions specified there (regardless of what `composer.json`
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-says).
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+This is important because the `install` command checks if a lock file is
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+present, and if it is, it downloads the versions specified there (regardless
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+of what `composer.json` says).
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-This means that anyone who sets up the project will download the exact
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-same version of the dependencies. Your CI server, production machines, other
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-developers in your team, everything and everyone runs on the same dependencies, which
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-mitigates the potential for bugs affecting only some parts of the deployments. Even if you
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-develop alone, in six months when reinstalling the project you can feel confident the
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-dependencies installed are still working even if your dependencies released
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-many new versions since then.
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+This means that anyone who sets up the project will download the exact same
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+version of the dependencies. Your CI server, production machines, other
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+developers in your team, everything and everyone runs on the same dependencies,
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+which mitigates the potential for bugs affecting only some parts of the
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+deployments. Even if you develop alone, in six months when reinstalling the
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+project you can feel confident the dependencies installed are still working even
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+if your dependencies released many new versions since then.
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If no `composer.lock` file exists, Composer will read the dependencies and
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-versions from `composer.json` and create the lock file after executing the `update` or the `install`
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-command.
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+versions from `composer.json` and create the lock file after executing the
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+`update` or the `install` command.
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-This means that if any of the dependencies get a new version, you won't get the updates
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-automatically. To update to the new version, use the `update` command. This will fetch
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-the latest matching versions (according to your `composer.json` file) and also update
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-the lock file with the new version.
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+This means that if any of the dependencies get a new version, you won't get the
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+updates automatically. To update to the new version, use the `update` command.
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+This will fetch the latest matching versions (according to your `composer.json`
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+file) and also update the lock file with the new version.
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```sh
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php composer.phar update
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```
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-> **Note:** Composer will display a Warning when executing an `install` command if
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- `composer.lock` and `composer.json` are not synchronized.
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-
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+> **Note:** Composer will display a Warning when executing an `install` command
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+> if `composer.lock` and `composer.json` are not synchronized.
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+
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If you only want to install or update one dependency, you can whitelist them:
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```sh
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php composer.phar update monolog/monolog [...]
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```
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-> **Note:** For libraries it is not necessarily recommended to commit the lock file,
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-> see also: [Libraries - Lock file](02-libraries.md#lock-file).
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+> **Note:** For libraries it is not necessarily recommended to commit the lock
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+> file, see also: [Libraries - Lock file](02-libraries.md#lock-file).
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## Packagist
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[Packagist](https://packagist.org/) is the main Composer repository. A Composer
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repository is basically a package source: a place where you can get packages
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from. Packagist aims to be the central repository that everybody uses. This
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-means that you can automatically `require` any package that is available
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-there.
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+means that you can automatically `require` any package that is available there.
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If you go to the [packagist website](https://packagist.org/) (packagist.org),
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you can browse and search for packages.
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Any open source project using Composer should publish their packages on
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-packagist. A library doesn't need to be on packagist to be used by Composer,
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-but it makes life quite a bit simpler.
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+packagist. A library doesn't need to be on packagist to be used by Composer, but
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+it makes life quite a bit simpler.
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## Autoloading
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For libraries that specify autoload information, Composer generates a
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-`vendor/autoload.php` file. You can simply include this file and you
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-will get autoloading for free.
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+`vendor/autoload.php` file. You can simply include this file and you will get
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+autoloading for free.
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```php
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require 'vendor/autoload.php';
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```
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-This makes it really easy to use third party code. For example: If your
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-project depends on monolog, you can just start using classes from it, and they
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-will be autoloaded.
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+This makes it really easy to use third party code. For example: If your project
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+depends on monolog, you can just start using classes from it, and they will be
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+autoloaded.
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```php
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$log = new Monolog\Logger('name');
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@@ -243,8 +210,8 @@ You define a mapping from namespaces to directories. The `src` directory would
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be in your project root, on the same level as `vendor` directory is. An example
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filename would be `src/Foo.php` containing an `Acme\Foo` class.
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-After adding the `autoload` field, you have to re-run `dump-autoload` to re-generate
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-the `vendor/autoload.php` file.
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+After adding the `autoload` field, you have to re-run `dump-autoload` to
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+re-generate the `vendor/autoload.php` file.
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Including that file will also return the autoloader instance, so you can store
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the return value of the include call in a variable and add more namespaces.
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@@ -256,11 +223,11 @@ $loader->add('Acme\\Test\\', __DIR__);
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```
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In addition to PSR-4 autoloading, classmap is also supported. This allows
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-classes to be autoloaded even if they do not conform to PSR-4. See the
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-[autoload reference](04-schema.md#autoload) for more details.
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+classes to be autoloaded even if they do not conform to PSR-4. See the [autoload
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+reference](04-schema.md#autoload) for more details.
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-> **Note:** Composer provides its own autoloader. If you don't want to use
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-that one, you can just include `vendor/composer/autoload_*.php` files,
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-which return associative arrays allowing you to configure your own autoloader.
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+> **Note:** Composer provides its own autoloader. If you don't want to use that
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+> one, you can just include `vendor/composer/autoload_*.php` files, which return
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+> associative arrays allowing you to configure your own autoloader.
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← [Intro](00-intro.md) | [Libraries](02-libraries.md) →
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Rob Bast