Strauss: The Better Mozart for WordPress Plugin Dependency Isolation

Originally published at recca0120.github.io

If you've read the }}">Mozart overview, you know what problem it solves: WordPress plugins share a PHP process, two plugins using different versions of the same library causes fatal errors, and Mozart prefixes your vendor namespaces to isolate them.

Strauss was forked from Mozart to address several of its known limitations. It's what the community generally recommends now.

What Strauss Changed

Installation

Recommended: PHAR

mkdir bin && touch bin/.gitkeep

Add to .gitignore:

bin/strauss.phar

Add to composer.json scripts:

{
  "scripts": {
    "prefix-namespaces": [
      "sh -c 'test -f ./bin/strauss.phar || curl -o bin/strauss.phar -L -C - https://github.com/BrianHenryIE/strauss/releases/latest/download/strauss.phar'",
      "@php bin/strauss.phar",
      "@composer dump-autoload"
    ],
    "post-install-cmd": ["@prefix-namespaces"],
    "post-update-cmd": ["@prefix-namespaces"]
  }
}

Downloads the PHAR on first run, uses the cached version after.

Or Require Directly

composer require --dev brianhenryie/strauss

Configuration

Strauss works with zero configuration — it infers the namespace prefix and target directory from your composer.json automatically.

To customize, add extra.strauss:

{
  "extra": {
    "strauss": {
      "target_directory": "vendor-prefixed",
      "namespace_prefix": "MyPlugin\\Vendor\\",
      "classmap_prefix": "MyPlugin_",
      "constant_prefix": "MYPLUGIN_",
      "packages": [
        "guzzlehttp/guzzle"
      ],
      "exclude_from_copy": {
        "packages": ["psr/container"],
        "namespaces": ["Psr\\Log\\"],
        "file_patterns": ["\\.md$"]
      },
      "exclude_from_prefix": {
        "namespaces": ["Psr\\"]
      }
    }
  }
}

Running

composer prefix-namespaces

Or directly:

php bin/strauss.phar

Dry run to preview changes without writing:

php bin/strauss.phar --dry-run

Constant Prefixing

Mozart doesn't handle define(). Strauss does:

// In your dependency
define('GUZZLE_VERSION', '7.0');

// After Strauss
define('MYPLUGIN_GUZZLE_VERSION', '7.0');

Constants are global just like classes — they conflict the same way. This matters for certain packages.

files Autoloader Support

Some packages use files autoloaders (direct require instead of PSR-4). Mozart handles these inconsistently. Strauss processes them fully:

// Package's composer.json
"autoload": {
    "files": ["src/functions.php"]
}

Strauss copies and prefixes these files without missing anything.

Loading in Your Plugin

// plugin.php
require_once __DIR__ . '/vendor-prefixed/autoload.php';

use MyPlugin\Vendor\GuzzleHttp\Client;

$client = new Client();

Or have Strauss inject the autoloader into vendor/autoload.php:

php bin/strauss.phar include-autoloader

Then you only need require vendor/autoload.php — no separate require for vendor-prefixed/.

License Compliance

Strauss adds a note to each modified file's header and preserves original license files. Mozart's handling of this is questionable — open source licenses typically require retaining original attribution. Strauss deals with it properly.

Mozart Configuration Compatibility

If you're currently using Mozart, Strauss reads extra.mozart config directly. No need to migrate immediately:

{
  "extra": {
    "mozart": {
      "dep_namespace": "MyPlugin\\Dependencies\\"
    }
  }
}

Strauss recognizes and applies it automatically.

Mozart or Strauss?

New project: use Strauss.

Existing Mozart project, consider migrating if:

• Your dependencies use files autoloaders
• You need define() constant prefixing
• License compliance matters
• You need function prefixing (v0.21.0+)

Migration cost is low — Strauss reads Mozart config, so it's mostly updating the scripts section.

Summary

Strauss and Mozart solve the same problem: WordPress plugin dependency conflicts. The difference is in the details: more complete autoloader support, constant prefixing, proper license handling, and safer defaults.

Start new plugins with Strauss. Migrate existing Mozart setups when you hit a limitation.

References

• Strauss GitHub Repository
• Composer Official Documentation
• WordPress Plugin Developer Handbook
• Mozart GitHub Repository (Strauss predecessor)