title: Regex Underscore between numbers
body: <pre><code>&lt;?php
      $string = '395095427174400_558374047513203';
      if(preg_match("/^[0-9][_][0-9]$/",$string)){
          echo "True";
      }else{
          echo "False";
      }
  ?&gt;
  </code></pre>
  
  <p>Why does my regex not match and underscore between numbers?</p>