Update en PDO

<?php
include'function.php';
$array = $_POST['arrayorder'];
 
if ($_POST['update'] == "update"){
  
 $count = 1;
 $cnx = Connexion();
 foreach ($array as $idval) {
  
	$req=$cnx->prepare ("UPDATE dragdrop SET listorder =".$count." WHERE id= ".$idval);
	$req->execute();
	return true;
	
  $count ++; 
 }
 echo 'All saved! refresh the page to see the changes';
}
?>