PHP RFC: Make the PHP core case-sensitive


This RFC is about making the PHP core case-sensitive.



Why ?

Detail of proposal by symbol type



Classes, interfaces, and trait names


Scope resolution operators

self, parent, static ->lowercase



Magic methods

lowercase except 'toString' ('tostring' and 'toString' are valid).

'Non-magic' Methods


Built-in constants

Remove support for case-insensitive constants. Remove CONST_CS flag.

Special cases for existing case-insensitive built-in constants. The following case-sensitive constants will be defined:

  • 'NULL', 'null', 'Null',
  • 'TRUE', 'true', 'True',
  • 'FALSE', 'false', 'False'

Every other case combination, like 'tRUE' or 'TrUe', will be considered as userspace constants.

User-defined constants



Other reserved names

'__halt_compiler' -> lowercase

Backward Incompatible Changes

Discussion and arguments

Proposed PHP Version(s)

List the proposed PHP versions that the feature will be included in. Use relative versions such as “next PHP 5.x” or “next PHP 5.x.y”.

RFC Impact


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

To Existing Extensions

To Opcache

New Constants

  • 'NULL', 'null', 'Null'
  • 'TRUE', 'true', 'True'
  • 'FALSE', 'false', 'False'

php.ini Defaults

If there are any php.ini settings then list:

  • hardcoded default values
  • php.ini-development values
  • php.ini-production values

Open Issues

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

Unaffected PHP Functionality

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.

Future Scope

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

Proposed Voting Choices

Include these so readers know where you are heading and can discuss the proposed voting options.

State whether this project requires a 2/3 or 50%+1 majority (see voting)

Patches and Tests

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.


After the project is implemented, this section should contain

  1. the version(s) it was merged to
  2. a link to the git commit(s)
  3. a link to the PHP manual entry for the feature


Links to external references, discussions or RFCs

Rejected Features

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

rfc/case-sensitivity.txt · Last modified: 2021/03/27 14:26 by ilutov