$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'mysitename.000webhostapp.com',
    'username' => 'XXXXX_username',
    'password' => 'password',
    'database' => 'XXXXX_dbname',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production'),
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array(),
    'save_queries' => TRUE
);

<?php
$servername = "mysitename.000webhostapp.com";
$username = "XXXXXX_username";
$password = "password";
$database = "XXXXXX_dbname";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$database", $username, $password);
    // set the PDO error mode to exception
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
    } catch(PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
    }
?>