This is a language change, so it will require an RFC.

Personally I'm against this as I don't see much use for it. I think if you are going to throw a deprecation warning, then I'd rather use the already existing E_USER_DEPRECATED with a custom message that can for example suggest alternatives.

The only reason a deprecated keyword would be a good idea is reflection (and therefore e.g. IDEs can strike-through those symbols). But most IDEs already respect @deprecated, so I don’t really see a use case for it. A good enough way to deprecate functions is to do this

/**
 * @deprecated
 */
function deprecated_function() {
    trigger_error("deprecated_function() is deprecated. Use undeprecated_function() instead", E_USER_DEPRECATED);
    ...
}

This is obviously just my opinion, so if you want to go on, an RFC would be the next step.

I know that it is already possible to throw a custom E_USER_DEPRECATED error. However, I think a deprecated modifier for functions would be a cleaner, faster and more obvious way of deprecating functions. If developers can simply add the ZEND_ACC_DEPRECATED flag to native functions, why should it not be possible for userspace functions too? Why do userspace developers need to throw an error themselves while a native function only needs a specific flag?

E_USER_DEPRECATED could rather be used for deprecating specific ways of calling a function or for deprecating whole libraries.

I've already requested write access to the Wiki in order to create an RFC but I am still waiting for the request to be accepted.

I have created an RFC at https://wiki.php.net/rfc/deprecated-modifier.

@pp3345 Could you please write a mail to internals about the RFC?

@pp3345 any news?

There was a discussion on php.internals about this, see http://news.php.net/php.internals/64435 - Though only some developers shared their opinions, most of them seemed to dislike the idea. However, we still could give it a try and move the RFC to voting.

Any news on how to move forward with this? Are you going to vote on this or is this PR obsolete now?

Ping @pp3345

@pp3345 Any news on that one? I personaly would really like this o.o

No news for more than a year, so I guess this is abandoned. If someone wants to pick it up, please take over the RFC and open the new pull req.