PHP PDO MySQL connection failing with 'Access denied' error, how to resolve?

Question

<?php

$dbhost_name = "localhost";
$database = "stmartia_pscsm";
$dbname = "root";
$dbpass = "";
//////// Do not Edit below /////////
try {
    $pdo = new PDO('mysql:host=localhost;dbname=' . $database, $dbname, $dbpass);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
    echo "Connection reussi !";
} catch (PDOException $e) {
    print "Error!: " . $e->getMessage() . "<br/>";
    die();
}
if (date_default_timezone_set('US/Eastern') == 0) {
    print "<!-- Error uknown timezone using UTC as default -->\n";
    date_default_timezone_set('UTC');
}

Error!: SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using password: NO)