<?php
$datos = array(
    'USERNAME' => 'root',
    'PASSWORD' => 'root'
);

$dsn = "mysql:unix_socket=/Applications/MAMP/tmp/mysql/mysql.sock;dbname=destinos;user=root;password=root;charset=utf8";

try {
    $conexion = new PDO($dsn, $datos['USERNAME'], $datos['PASSWORD']);

} catch(PDOException $e) {
    echo "Error: " . $e->getMessage();
}