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Writing Composer Scripts Safely

Composer scripts execute commands with the installing user's permissions, so script definitions and plugins must be reviewed before running them.

1 views Published Oct 17, 2026 Updated Oct 17, 2026 admin

Composer scripts execute commands with the installing user's permissions, so script definitions and plugins must be reviewed before running them.

What It Does


Keep scripts simple, documented, and limited to reviewed commands. Validate package metadata and build optimized autoload maps. Disable arbitrary package script execution when inspecting untrusted projects.

Requirements and Compatibility


Use a supported PHP runtime and install any third-party tool or extension explicitly shown in the examples. Commands should be run from the project root unless stated otherwise.

Syntax, Inputs and Results


The examples separate configuration, the smallest working operation and a realistic follow-up task. Adapt file paths and dependency versions to your own project.

Example 1: Basic Use


Keep scripts simple, documented, and limited to reviewed commands.

{
  "scripts": {"lint": "@php -l src/bootstrap.php", "check": "@lint"},
  "scripts-descriptions": {"check": "Run reviewed local checks"}
}

Example 2: Another Case


Validate package metadata and build optimized autoload maps. Disable arbitrary package script execution when inspecting untrusted projects.

composer validate --strict
composer dump-autoload -o
composer install --no-scripts

Practical Example


Install the exact locked versions and verify the target PHP runtime. Disable arbitrary package script execution when inspecting untrusted projects.

composer install --no-interaction --prefer-dist
composer check-platform-reqs
composer install --no-scripts

For production, apply the compatibility and edge-case limits described below.

Important Behavior and Edge Cases


Use the checked-in lock file for reproducible application builds.

Comparison with Related Functions and Tools


SubjectKey difference
composer install vs composer updateinstall follows composer.lock; update resolves new versions and updates the lock file.

Common Beginner Mistakes


MistakeCorrect approach
Treating a version range as a fixed installed versionCommit composer.lock for applications and run composer install in deployment.
Skipping the prerequisite of this specific workflowInstall or configure the named tool and confirm the example can actually run.
Ignoring edge conditionsUse the checked-in lock file for reproducible application builds.

Key Takeaways


  • Composer scripts execute commands with the installing user's permissions, so script definitions and plugins must be reviewed before running them.
  • Use the checked-in lock file for reproducible application builds.
  • Keep application configuration, source code and validation tests under version control.

Use these examples as a starting point, then validate the result with the actual PHP build, dependencies and inputs used by your application.

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