title: Laravel regular expression whitespace
body: <pre><code>$rules = array(
    'password' =&gt; array(
                    'required',
                    'min:6',
                    'regex:/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*(_|[^\w])).+$/')
  );
  </code></pre>
  
  <p>I am using this regular expression to allow (Contain at least one uppercase/lowercase letters and one number) </p>
  
  <p>but I need help to validate that have only one whitespace (so continue whitespace makes invalid) </p>