PHP RFC: instanceof improvements

• Version: 1.0
• Date: 2020-05-17
• Author: Max Semenik, maxsem.wiki@gmail.com
• Status: Draft
• First Published at: http://wiki.php.net/rfc/instanceof_improvements

The elevator pitch for the RFC. The first paragraph of this section will be slightly larger to give it emphasis; please write a good introduction.

I'd like to propose to modify instanceof to support non-object types, as well as expressions on the right:

'foo' instanceof string            // true
'foo' instanceof 'string'          // true
$logger instanceof "{$this->loggerType}Logger"
$foo instanceof SomeClass::class   // kinda silly - but why the heck not?
$foo instanceof $someObject::class // a less silly variation

What breaks, and what is the justification for it?

PHP 8.0.

Describe the impact to CLI, Development web server, embedded PHP etc.

Will existing extensions be affected?

It is necessary to develop RFC's with opcache in mind, since opcache is a core extension distributed with PHP.

Please explain how you have verified your RFC's compatibility with opcache.

Describe any new constants so they can be accurately and comprehensively explained in the PHP documentation.

Make sure there are no open issues when the vote starts!

List existing areas/features of PHP that will not be changed by the RFC.

This helps avoid any ambiguity, shows that you have thought deeply about the RFC's impact, and helps reduces mail list noise.

This section details areas where the feature might be improved in future, but that are not currently proposed in this RFC.

What should be done about this (improve instanceof / add new operator / reject this RFC)?

Links to any external patches and tests go here.

If there is no patch, make it clear who will create a patch, or whether a volunteer to help with implementation is needed.

Make it clear if the patch is intended to be the final patch, or is just a prototype.

For changes affecting the core language, you should also provide a patch for the language specification.

After the project is implemented, this section should contain

1. the version(s) it was merged into
2. a link to the git commit(s)
3. a link to the PHP manual entry for the feature
4. a link to the language specification section (if any)

Links to external references, discussions or RFCs

Keep this updated with features that were discussed on the mail lists.