php mysql coding error : plz tell me that where is error..... i am in tention due to this,..

**Fatal error:** Uncaught Error: Call to undefined function mysql_connect() in C:\xampp\htdocs\kalooo1\includes\db.php:2 Stack trace: #0 C:\xampp\htdocs\kalooo1\index.php(21): include() #1 {main} thrown in C:\xampp\htdocs\kalooo1\includes\db.php on line 2 

**db.php**

    <?php
mysql_connect("localhost","root","");``
mysql_select_db("kalooo");
?>

**index.php(21)**

include("includes/db.php");