title: Convert multidimensional array to dot notation in Symfony2
body: <p>Symfony converts nested YAML and PHP array translation files to a dot notation, like this: <code>modules.module.title</code>.</p>
  
  <p>I'm writing some code that exports YAML translation files to a database, and I need to flatten the parsed files to a dot notation.</p>
  
  <p><strong>Does anyone know which function Symfony uses to flatten nested arrays to dot notation?</strong> </p>
  
  <p>I cannot find it anywhere in the source code.</p>