title: How to change Wordpress language conditionally?
body: <p>Is there any way to change the Wordpress language conditionally? I mean let's say we have a variable <code>$theme_lang</code> and if that is equal to something, change the language across the theme. 
  Here's the code:</p>
  
  <pre><code>if($theme_lang == 'de'){
   //everything goes here in German
  }
  </code></pre>
  
  <p>In short, I want to avoid a separate installation for another language. Thanks!</p>