title: how to calculate what is date after 10 days in php?
body: <p>Suppose the <code>$start_date = 2017-12-13</code>.</p>
  
  <p>And i want to know what should be date after 10 days.</p>
  
  <p>i tried this <code>strtotime("$start_date +10 days")</code> and the output is <code>1512946800</code> </p>