title: PHP regular expression start and end with given strings
body: <p>I have a string like this 
  <code>05/15/2015 09:19 PM pt_Product2017.9.abc.swl.px64_kor_7700</code> I need to select the <code>pt_Product2017.9.abc.swl.px64_kor</code> from that. (start with <code>pt_</code> and end with <code>_kor</code>)</p>
  
  <pre><code>$str = "05/15/2015 09:19 PM pt_Product2017.9.abc.swl.px64_kor_7700";
  preg_match('/^pt_*_kor$/',$str, $matches);
  </code></pre>
  
  <p>But it doesn't work.</p>