The RFC proposes to deprecate the listed functionality in PHP 8.6 and remove it in PHP 9 (except where otherwise noted).
Deprecate the list() construct?
Deprecate returning from a finally block?
Deprecate using let as an identifier?
Deprecate using namespace as a class constant name?
Deprecate using in, out, and inout as identifiers?
Deprecate using is as an identifier?
Deprecate the possibility to name a function readonly?
Deprecate using _ as a constant and compile time alias?
Deprecate using _ as a function name and the _() function alias for gettext()?
Passing objects for $array parameter of array_walk() and array_walk_recursive()?
Passing objects for $options parameter of deflate_init() and inflate_init()?
Passing objects as parameters to the zlib.inflate and zlib.deflate stream filters?
Passing objects as parameters to the bzip2.decompress and bzip2.compress stream filters?
Passing objects for $vars parameter of mb_convert_variables()?
Passing objects for $data parameter of http_build_query()?
Deprecate define() with $case_insensitive being specified?
Deprecate is_subclass_of with string when $allow_string is false?
Deprecate is_a with string when $allow_string is false?
Deprecate SORT_LOCALE_STRING flag for sort() functions?
Deprecate Metaphone Function?
Deprecate dechunk filter?
Deprecate ReflectionProperty::setValue() and ReflectionProperty::setRawValue() with wrong types?
Deprecate ReflectionMethod::invoke() and ReflectionMethod::invokeArgs() with objects for static methods?
Deprecate ArrayIterator methods that inherit ArrayObject implementation?
Deprecate spl_object_hash()?
Deprecate SplFileObject CSV methods?
Deprecate mysqli::stmt_init, mysqli_stmt_init, and mysqli_stmt::__construct without the second argument?
Deprecate mysqli_get_charset()?
Deprecate passing a $sessionhandler object to session_set_save_handler() which does not contain the create_sid() and validateId() methods?