function DB()
{
    $db = readConfigurationFile();
    // Create connection
    $conn = mysql_connect($db['servername'], $db['username'], $db['password']);
    // Check connection
    if (!$conn) {
        $error = mysql_error();
        echo '{"error" : $error}';
        exit;
    }
    if (!mysql_select_db($db['databasename'], $conn)) {
        echo '{"error" : "Could not select database"}';
        exit;
    }
    return $conn;
}
<?php

require_once __DIR__ . '/../backend/index.php';
$backend = getBackend();
$backend->bootstrap(readConfigurationFile());
$backend->processRequest($_SERVER, \array_merge($_GET, $_POST));