====== PHP RFC: Deprecations for PHP 8.7 ======
  * Date: 2026-08-12
  * Authors:
    * Daniel Scherzer <daniel.e.scherzer@gmail.com>
  * Status: Draft
  * Discussion thread: Not started yet
  * Voting thread: tbd

===== Introduction =====

The RFC proposes to deprecate the listed functionality in PHP 8.7 and remove it in PHP 9 (except where otherwise noted).

The following list provides a short overview of the functionality targeted for deprecation, while more detailed explanation is provided in the Proposal section:

  * Deprecate <php>is_a</php> with $object_or_class not being a string or object
  * Deprecate <php>is_subclass_of</php> with $object_or_class not being a string or object

===== Proposals =====

Each feature proposed for deprecation is voted separately and requires a 2/3 majority.
All votes refer to deprecation in PHP 8.7 and removal in PHP 9 (except where otherwise noted).

==== Example Deprecation ====

  * Author: Name <name@example.com>

Description

==== Deprecate is_a() with $object_or_class not being a string or object ====

  * Author: Daniel Scherzer <daniel.e.scherzer@gmail.com>

<php>is_a</php> is used to check if an object or class name is an instance of some other named class/interface. The first parameter can be either an object to check, or the name of a class. It can also be something other than a string or object, in which case the function will always return false. I.e. code like <php>is_a(5, "int")</php> or <php>is_a(true, "bool")</php> will always return false.

Given that <php>is_a</php> always returns false when the first parameter is something other than a string or object, we propose to deprecate providing non-string non-object parameters. If the type of a parameter is not known, the <php>is_a</php> call can be preceded with a call to <php>is_object</php>.

If accepted, calling <php>is_a</php> with non-string non-object parameters will emit a deprecation similar to the following:

<blockquote>
Deprecated: Calling is_a() with $object_or_class of type %s is deprecated.
</blockquote>

==== Deprecate is_subclass_of() with $object_or_class not being a string or object ====

  * Author: Daniel Scherzer <daniel.e.scherzer@gmail.com>

<php>is_subclass_of</php> is used to check if an object or class name is an instance of a subclass of some other named class, or an instance of an interface. It works similarly to <php>is_a</php>, except when an object's class is the exact same as the class to check. Like <php>is_a</php>, the first parameter can be either an object to check, or the name of a class. It can also be something other than a string or object, in which case the function will always return false. I.e. code like <php>is_subclass_of(5, "int")</php> or <php>is_subclass_of(true, "bool")</php> will always return false.

Given that <php>is_subclass_of</php> always returns false when the first parameter is something other than a string or object, we propose to deprecate providing non-string non-object parameters. If the type of a parameter is not known, the <php>is_subclass_of</php> call can be preceded with a call to <php>is_object</php>.

Unlike <php>is_a</php>, <php>is_subclass_of</php> also semantically makes no sense for non objects (or string class names) because there is no subclassing concept for non-objects.

If accepted, calling <php>is_subclass_of</php> with non-string non-object parameters will emit a deprecation similar to the following:

<blockquote>
Deprecated: Calling is_subclass_of() with $object_or_class of type %s is deprecated.
</blockquote>