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PHP RFC: Objects as hash keys
- Version: 0.9
- Date: 2014-10-21
- Author: Stas Malyshev (firstname.lastname@example.org)
- Status: Draft
- First Published at: http://wiki.php.net/rfc/objkey
The purpose of this RFC is to introduce a magic method that will allow objects to serve as hash keys.
In PHP array keys can be only represented as numbers and strings. However, there already are several classes that represent different kinds of numbers (such as GMP objects) and some objects can also represent strings (e.g. Unicode strings) or string-like objects. It would be convenient to be able to use such objects as array keys to.
It could be achieved as conversion to string, but this is not ideal since object's string representation does not always match object's identity and there may be case where human-readable string may be different from value for the purposes of hashing.
Create a new magic method, __hash() which is called when object is supplied as a hash key, and returns string or integer that is used as the hash key.
A number of languages implement the same facility, namely:
- Java has hashCode() and toString()
- Python has __str__, __repr__ and __hash__
- Ruby has object.hash
Backward Incompatible Changes
Should not break anything as we don't allow this now.
Proposed PHP Version(s)
Targeted for PHP 7
No impact on SAPIs
To Existing Extensions
If somebody implements something like ArrayAccess they may want to update it to accommodate objects.
Since objects are run-time, should not have any effects on opcache.
Proposed Voting Choices
New magic method requires 2/3 majority.
Patches and Tests