title: Extract numbers in PHP from a string + ignoring the <sup> content
body: <p>I have 2 type of strings:</p>
  
  <ol>
  <li>356 Hello World!</li>
  <li>6 Hello France! <sup>2,5</sup></li>
  </ol>
  
  <p>I use this code to extract the number, I actually need only the numbers from the begining</p>
  
  <pre><code>$int_image_id = (int) filter_var(get_the_title(), FILTER_SANITIZE_NUMBER_INT);
  </code></pre>
  
  <p>the result is:</p>
  
  <ol>
  <li>356</li>
  <li>625 (but it should be 6)</li>
  </ol>