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composer.json is a JSON file placed in the root folder of PHP project. Its purpose is to specify a common project properties, meta data and dependencies, and it is a part of vast array of existing projects. In most ways, it is a counterpart to .NET project file. At least, the information from the composer.json file can be represented by standard .NET project properties and items (not the other way around).


By default, the composer.json file is processed during build time. As a result, certain composer metadata is mapped to the corresponding project properties, thanks to which the created NuGet packages are automatically annotated.

Following table lists composer meta and corresponding project properties being automatically set:

Meta MsBuild Property Nuspec Value
"name" PackageId Id
"description" PackageDescription Description
"version" Version, PackageVersion /1/ Version
"license" PackageLicenseExpression license
"homepage" PackageProjectUrl ProjectUrl
"authors" Authors Authors

/1/ Version respects specified $(VersionSuffix) property. In case project has non-empty VersionSuffix, the resulting Version will have the suffix specified even composer's version meta does not have it.

MSBuild Properties#


The ComposerJsonPath property controls path to the composer.json file. If the property is empty, the file is being located next to the project file implicitly.


Set ComposerJsonPath to false in order to disable processing of composer.json meta data during build.


Setting ComposerAutoload to true or false controls whether autoload rules are processed.


Explicitly setting VersionSuffix allows to override suffix portion of version meta data from composer file. If VersionSuffix is non-empty string, the resulting version will respect the suffix.

Project file:



    "version": "1.2.3"

The setup above results in PackageVersion property set to 1.2.3-dev.

Composer Dependencies#

Sections "require", "require-dev" and "suggest" are not processed (yet).

Composer Autoload#

Composer autoloading provides standard approach in defining classes automatically. Compiler processes the "autoload" section and tries to avoid autoloading process in the first place. Classes, interfaces and traits fulfiling the specified rules are declared implicitly without need of invoking autoloaders during run time.

In case a source file contains more than just the class itself, autoloading cannot be fully optimized. In such case, containing source file has to be looked up and invoked during run time causing an unnecesary overhead.

Available since 0.9.980

Sample "composer.json":

    "autoload": {
        "psr-4": {
            "Vendor\\Namespace\\": "src/",
            "": "src/",
        "psr-0": {
            "Vendor\\Namespace\\": "src/",
            "Vendor_Namespace_": "src/"
        "classmap": ["src/", "lib/", "Something.php"],
        "exclude-from-classmap": ["/src/Tests/", "/lib/tests/"]

This behavior differs from standard PHP where the map above is used to generate autoloaders which are invoked every time when an unknown class, interface or trait is being used in every new web request.