Strauss: The Better Mozart for WordPress Plugin Dependency Isolation

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

Issue	Mozart	Strauss
`files` autoloader support	Limited	Full
Constant prefixing (`define()`)	Not supported	Supported
Function prefixing	Not supported	v0.21.0+
License compliance	Questionable	Header edits + license files preserved
Destructive defaults	Can delete files	Non-destructive by default
Zero config	Requires setup	Works out of the box
Test coverage	Limited	Comprehensive PHPUnit tests

Installation

Recommended: PHAR

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mkdir bin && touch bin/.gitkeep

Add to .gitignore:

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bin/strauss.phar

Add to composer.json scripts:

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{
  "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

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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:

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{
  "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\\"]
      }
    }
  }
}

Option	Purpose
`target_directory`	Where processed files go (default: `vendor-prefixed`)
`namespace_prefix`	Prefix added to namespaces
`classmap_prefix`	Prefix for classes without namespaces
`constant_prefix`	Prefix for `define()` constants
`exclude_from_copy`	Packages, namespaces, or file patterns to skip entirely
`exclude_from_prefix`	Copy but don’t prefix (e.g. PSR interfaces)

Running

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composer prefix-namespaces

Or directly:

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php bin/strauss.phar

Dry run to preview changes without writing:

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php bin/strauss.phar --dry-run

Constant Prefixing

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

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// 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:

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

Strauss copies and prefixes these files without missing anything.

Loading in Your Plugin

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// 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:

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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:

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{
  "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.