title: php check if a string contains special character and split the character
body: <p>I have a string <code>classone insertclass_182 classtwo</code>.</p>
  
  <p>I want to check if the string contains <code>insertclass_</code> And if the string contains <code>insertclass_</code>, I want to save the Numbers after the sign <code>_</code> in a variable. In this case: 182. But the number also can be another number ... for example <code>insertclass_4</code></p>
  
  <p>Thanks!</p>