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Date: Mon, 11 Dec 2017 04:03:46 +0100
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To: PHP internals <internals@lists.php.net>
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Subject: Re: Add \Reflection*::getHash()
From: andreas@dqxtech.net (Andreas Hennings)

So far this proposal only discusses reflections of PHP declarations / symbols.

What would we do for e.g. ReflectionObject?
Return the spl_object_hash()?
Or return the hash of the instantiated class?
Or a hash of the serialized object?
We need to return something, because ReflectionObject extends ReflectionClass.


On 11 December 2017 at 03:11, Andreas Hennings <andreas@dqxtech.net> wrote:
> I propose to add a new method ::getHash() to reflection API classes.
>
> Such that:
>
> Two reflectors return the same hash, if and only if:
>
> 1. the reflected items have the same type (class, method, parameter etc), AND.
> 2. the reflected items have the same names, AND.
> 3. the reflected items have the same PHP code (e.g. for distinct
> processes), AND.
> 4. optionally: Every base class, every implemented interface and every
> used trait has the same PHP code (and thus, the same hash).
> 5. optionally: The PHP version and PHP settings are the same. (*)
>
> Such an id can be used as a cache key between requests.
>
> It would automatically change / become invalid, if:
> - new code changes are deployed, OR.
> - different processes include different files that each declare the
> same class, OR.
> - php is upgraded, or php settings change. (*)
>
> Currently the best way (for practicality and performance) to achieve
> something like this is to get the timestamp of the file that defines
> the class.
>
> Note: The behavior of a function can change if the code of another
> function that is being called is modified.
> The hash would still be the same, because it does not look at
> functions being called.
>
> (*) Maybe for the php version and settings there should instead be a
> global hash, which can be used as salt for a combined cache key.
>
>
> I was first going to propose to add this new method directly on
> \Reflector interface.
> But this would be a BC break, because userland classes that implement
> this interface would break.
>
> So instead, either
> - add it to each class separately, or
> - add a new interface \Reflector2 extends \Reflector (yeah, versioned
> interfaces!), and let all reflection classes implement that.