title: how to get the value of checksum in php header
body: <p>I have a header in php which contains a link like</p>
  
  <pre><code>&lt;?php
  header("Location: "."https://abc.com/ppp/purchase.do?version=3.0&amp;".
      "merchant_id=&lt;23255&gt;&amp;merchant_site_id&lt;21312&gt;&amp;total_amount=&lt;69.99&gt;&amp;".
      "currency=&lt;USD&gt;&amp;item_name_1=&lt;incidentsupporttier1&gt;&amp;item_amount_1=&lt;1&gt;&amp;".
      "time_stamp=&lt;2010-06-14.14:34:33&gt;&amp;**checksum=&lt;calculated_checksum&gt;**");
  ?&gt;
  </code></pre>
  
  <p>when i run this page the value of checksum is calculated and the link is opened</p>
  
  <p>now how checksum is calculated?
  calculated_checksum=md5(abc);</p>
  
  <p>md5 is an algorithm which calculates the value of checksum based on certain values inside the bracket.</p>
  
  <p>now i want to know how can i pass the value of checksum in the header url  </p>