src/Autoloader.php
public static function findComposerAutoloaderVendorDir(string $composer_loader_class)
    {
        $ref = new \ReflectionClass($composer_loader_class);

        // Composer is located at MyProject/vendor/composer
        $path = dirname($ref->getFileName());
        return dirname($path);
    }
public static function findComposerAutoloaderVendorDir(string $composer_loader_class)
    {
        $ref = new \ReflectionClass($composer_loader_class);

        // Composer is located at MyProject/vendor/composer
        $path = dirname($ref->getFileName());
        return dirname($path);
    }
Get the Composer vendor directory, using the Composer autoloader class
name provided.

@param string $composer_loader_class The fully qualified class name of the Composer autoloader
@return string The vendor dir used by composer