title: PHP change anything that is not a letter or a number to `%20`
body: <p>I need to use PHP to change anything that is not a letter or a number to <code>%20</code>.</p>
  
  <p>For example: <code>$_POST['name'] = "John_Doe"</code> or <code>$_POST['name'] = "John-Doe"</code> would become <code>John Doe</code>.</p>
  
  <p>Is there some regex that can be used that would replace anything that is not a letter or a number?</p>