PHP follows the typical client-server model. Every page request initiates your application; you load configuration parameters, connect to a database, fetch information and render HTML. A Node.js app runs permanently and it need only initialize once. For example, you could create a single database connection object which is reused by everyone during every request. Admittedly, there are ways to implement this type of behavior in PHP using systems such as Memcached but it’s not a standard feature of the language.