fetch row information

I have a simple upload script. The primary key "id_ref" has an "auto increment" property.
What I would like to do is insert the new row then immediately retrieve the id_ref from that new row so it can be echoed on the page.. IE Your information has been uploaded. Your reference number is "echo the id_ref".
Help appreciated.
N

<?php

function db_connect() {
   $result = new mysqli('localhost', 'demo', 'password', 'demo');
   if (!$result) {
     throw new Exception('Could not connect to database server');
   } else {
     return $result;
   }
}

?>


<?php
 $conn = db_connect();
  $result = $conn->query("insert into myTable values
                         ('', '".$date."','".$_SESSION['trading']."','".$_SESSION['title']."')");

?>

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