title: Regular expression to preserve line breaks
body: <p>I have a regular expression which allows only certain characters in the message.
  What I'm trying to achieve is to <strong>allow line breaks</strong> as well which will be preserved using <strong>nl2br</strong> function.</p>
  
  <p>That's what I have so far:</p>
  
  <pre><code>preg_replace('/[^a-zA-Z0-9ńśćółęążź\ .,-]/','',$message)
  </code></pre>
  
  <p>As far as I have checked, the following expression should preserve line breaks but I'm having problems adding it to the above expression:</p>
  
  <pre><code>/(\r|\n|\r\n){2,}/
  </code></pre>