php - Deprecated: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead

Im developed PHP user login and registration system, i have a displayed always this error in my local host , how to fix it?

Deprecated: mysql_connect(): The mysql extension is deprecated and
will be removed in the future: use mysqli or PDO instead
(C:\wamp\www\registerations\db.php on line 9)

this is my code
db.php

$connection = mysql_connect('localhost', 'root', '');
if (!$connection){
    die("Database Connection Failed" . mysql_error());
}
$select_db = mysql_select_db('register');
if (!$select_db){
    die("Database Selection Failed" . mysql_error());
}
?>

Answer

  $con = mysqli_connect("localhost","root","","register");

// Check connection
if (mysqli_connect_errno())
 {
 echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

?> 

// try this..