How to detect if iPhone has retina display or not?

Question

How can I detect if an iPhone has a retina display or not? Is there a reliable way? Either pure PHP or preferably Zend Framework way of doing this.

Answer 1

i figure it out by this

var retina = window.devicePixelRatio > 1;

if (retina)
{
    // the user has a retina display
}
else
{
    // the user has a non-retina display
}