title: Regex to insert dot (.) after characters, before new line
body: <p>I'm reformatting some text, and sometimes I have a string, where there is a sentence which is not ended by a dot.</p>
  
  <p>I'm running various checks for this purpose, and one more I'd like is to <strong>"Add dot after last character before new line"</strong>.</p>
  
  <p>I'm not sure how to form the regular expression for this:]</p>
  
  <pre><code>$string = preg_replace("/???/", ".\n", $string);
  </code></pre>