Using Rockettheme's Locator and Stream classes

composer.json

{
    "require": {
        "php": ">=5.4.0",
        "rockettheme/toolbox": "1.3.0"
    }
}

example.php

<?php
    use RocketTheme\Toolbox\ResourceLocator\UniformResourceLocator;
    use RocketTheme\Toolbox\StreamWrapper\StreamBuilder;
    use RocketTheme\Toolbox\StreamWrapper\ReadOnlyStream;
    
    // Initialize locator
    $locator = new UniformResourceLocator(UserFrosting\APP_DIR);
    $locator->addPath('assets', '', 'system/assets');
    $locator->addPath('assets', '', 'user/assets');
    
    // Use locator to initialize streams
    ReadOnlyStream::setLocator($locator);
    $sb = new StreamBuilder([
        'assets' => '\\RocketTheme\\Toolbox\\StreamWrapper\\ReadOnlyStream'
    ]);

    echo file_get_contents('assets://css/theme.css');