calculate an unique id from an array/class

Question

I use a data class to feed templates my data, I want to calculate a unique id from the data in the data class so I can check if the template with that data is already in cache and then serve that version.

so a function to get an unique id from an array of a class would help me out.

something like this works but is rather costly md5(serialize($classdata))

I'm hoping there is some function to get the unique id without serializing all data, or at least not to have to in php.

edit:
I celebrated too soon, the unique id is only the same in the current instance a restart of the same script makes another id, which then of course is not in cache.

testscript used:

<?php
class foo {}
$f = new foo;
print spl_object_hash($f);

I'll explain in some more depth

class template_data implements IteratorAggregate, ArrayAccess, Countable {
    
    private $_data;
    
    //some methods for the overloaded classes
    //
    
    //the getId function
    public function getId() {
        return hash('md5',serialize($this->_data));
    }
    
}

$t = new template('file');
$d = new template_data('some data');
$t->addData($d);
$t->display();

Now if the data given to the template engine is in cache it uses that version preventing to having to re-parse the template for the dataset.

This is a simplistic view of the template_data, it is actually lazy loading and uses memcached dataid's so the data isn't actually fetched till it is used in the template.

Answer 1

You could try spl_object_hash()

From the docs

This function returns a unique identifier for the object. This id can be used as a hash key for storing objects or for identifying an object.