The RFC proposes to deprecate the listed functionality in PHP 8.5 and remove it in PHP 9 (except where otherwise noted).
Deprecate semicolon-terminated case statements?
Deprecate non-standard cast names?
Deprecate attributes applying to multiple class properties/constants
Deprecate backticks as an alias for shell_exec?
Deprecate the __sleep() and __wakeup() magic methods?
Deprecate using values null as an array offset and when calling array_key_exists()?
Deprecate __debugInfo() returning null?
Deprecate constant redeclaration?
Deprecate closure binding issues?
Enact follow-up phase of the Path to Saner Increment/Decrement operators RFC?
Deprecate the report_memleaks INI directive?
Deprecate the register_argc_argv INI directive and make in default to Off in PHP 8.5, then hardcode it to Off for all non-CLI-related SAPIs on PHP 9 (while keeping it hardcoded to On for CLI-related ones)?
Remove disable_classes INI setting?
Deprecate Reflection*::setAccessible()?
Deprecate ReflectionParameter::allowsNull()?
Deprecate ReflectionClass::getConstant() for missing constants?
Deprecate ReflectionProperty::getDefaultValue() for properties without default values?
Deprecate ArrayObject and ArrayIterator with objects?
Deprecate SplObjectStorage::contains(), SplObjectStorage::attach(), and SplObjectStorage::detach()?
Deprecate passing spl_autoload_call() to spl_autoload_unregister()?
Deprecate non-canonical type names for settype()?
Deprecate the $exclude_disabled parameter of get_defined_functions()?
Deprecate passing null to readdir(), rewinddir(), and closedir()?
Deprecate passing string which are not one byte long to ord()?
Deprecate passing integers outside the interval [0, 255] to chr()?
Formally deprecate socket_set_timeout?
Deprecate the $http_response_header predefined variable?
Deprecate FILTER_DEFAULT constant?
Emit a deprecation notice when using the default value for the $filter argument of the filter_*() functions?
Deprecate special build system support for drivers without a driver manager?
Deprecate ODBCVER checks?
Deprecate PDO’s uri: scheme?
Deprecate PDO::ERRMODE_WARNING constant?
Deprecate driver specific PDO constants and methods?
Deprecate statement transaction state specific PDO constants?
Deprecate xml_parser_free()?
Deprecate curl_share_close()?
Deprecate imagedestroy()?
Deprecate key_length parameter of openssl_pkey_derive()?
Deprecate intl.error_level INI setting?
Formally deprecate mysqli_execute?
Deprecate building ext/ldap against Oracle LDAP?
Deprecate the $context parameter for finfo_buffer()?
Deprecate DATE_RFC7231 and DateTimeInterface::RFC7231?