title: PHP Regex convert plain text URL to link unless it already is
body: <p>I have a php string $tweet that looks like this...</p>
  
  <pre><code>This is a sample tweet https://tr.co/sdfhnjn3
  </code></pre>
  
  <p>But sometimes it can look like this...</p>
  
  <pre><code>This is a sample tweet &lt;a href="https://tr.co/sdfhnjn3"&gt;https://tr.co/sdfhnjn3&lt;/a&gt;
  </code></pre>
  
  <p>I am wanting to convert all <a href="https://tr.co" rel="nofollow noreferrer">https://tr.co</a> links to actual a href links unless they are already in that format.</p>
  
  <p>I know I can convert the links with Regex but can I also check if they are already a link using it as well?</p>