Deleting MySQL Row Content

<?php
  $host = 'host';
  $user = 'user';
  $pass = 'pass';
  $db = 'db';
  try { 
    $conn = new PDO("mysql:host=$host;dbname=$db",$user,$pass);      	
    // set the PDO error mode to exception 
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);    
    // sql to delete a record  
    $sql= "DELETE FROM users WHERE user_id=3";  
    // use exec() because no results are returned    
    $conn->exec($sql);      	
    echo "Record deleted successfully";
  } catch(PDOException $e) {      	
    echo $sql . "<br>" . $e->getMessage();
  }
  $conn = null;  
?>