Cakephp-Routes-2.php

<?php
//url /blog/3_articolo-di-esempio
Router::connect(
    'blog/:id_:slug',
    array(
        'controller' => 'posts',
        'action' => 'view'
    ),
    array(
        'pass' => array('id'),
        'id' => '[0-9]+',
    )
);

//url /blog/3/articolo-di-esempio
Router::connect(
    'blog/:id/*',
    array(
        'controller' => 'posts',
        'action' => 'view'
    ),
    array(
        'pass' => array('id'),
        'id' => '[0-9]+',
    )
);