title: PHP convert string into date time
body: <p>I have a php string from db it is <code>20/11/2017</code> I want to convert it milliseconds. 
  It's my code to doing that. </p>
  
  <pre><code>$the_date = "20/11/2017";
  $mill_sec_date = strtotime($the_date);
  var_dump($mill_sec_date);
  </code></pre>
  
  <p>But it does not print any thing rather than </p>
  
  <pre><code>bool(false);
  </code></pre>
  
  <p>What is the problem and how can i solve it ???? </p>