title: PHP preg_replace special characters
body: <p>I am wanting to replace all non letter and number characters i.e. <code>/&amp;%#$</code> etc with an underscore <code>(_)</code> and replace all <code>'</code> (single quotes) with "<code></code>"blank (so no underscore).</p>
  
  <p>So "<strong>There wouldn't be any</strong>" (ignore the double quotes) would become "<strong>There_wouldnt_be_any</strong>".</p>
  
  <p>I am useless at reg expressions hence the post.</p>
  
  <p>Cheers</p>