Levi Morrison


PHP RFC: Reserve More Types in PHP 7


This RFC prevents the use of the following words to be used as a class, interface or trait name:

  • int
  • float
  • bool
  • string
  • true, false
  • null

This RFC does not fully reserve them as keywords; it only prohibits their usage as class, interface and trait names. It also prevents them from being used in namespaces.

I have chosen to not reserve integer, double and boolean out of interest of proposing the smallest useful subset. Another RFC could reserve these aliases in the future.


Facilitate Future RFCs

Reserving these words in PHP 7 would allow for another RFC to add scalar types in a minor release such as PHP 7.1 (assuming they make no backwards compatibility breaks). Without reserving them now a future RFC would only be able to target major PHP versions such as version 8 since they would break backwards compatibility.

Disallowing Classes

Given that PHP has primitive types such as int, float, string and null it does not make sense for them to exist as classes, or if they do they should be provided by PHP itself.

Backward Incompatible Changes

This breaks any and all cases where these new reserved words are used in class, interface or trait names. It does not break any usages as function or method names or as class constants.

Unaffected PHP Functionality

This RFC does not change the way our current parameter and return type hints work. Support for these new reserved words as types for parameters or return types is beyond the scope of this RFC.

Future Scope

Potentially future RFCs could:

  • reserve the aliases of these types, such as integer, double and boolean
  • add explicit scalar type support for parameter and return types
  • add union types, such as int|false
  • reserve other types such as numeric, mixed or scalar

Patches and Tests

There is currently no implementation.

Version History

  • 1.0: Reserve int, integer, float, double, bool, boolean, string, true, false, null
  • 1.1: No longer reserve integer, double and boolean


An option needs 50%+1 votes to win

reserve_more_types_in_php_7 (95.2% approved)
User Vote
ajf Yes
bishop Yes
bwoebi Yes
Damien Tournoud Yes
danack Yes
daverandom Yes
derick Yes
dmitry No
fredemmott Yes
frozenfire Yes
galvao Yes
guilhermeblanco Yes
indeyets Yes
irker Yes
jedibc Yes
jgmdev Yes
jmikola Yes
jwage Yes
kalle No
kguest Yes
kinncj Yes
lcobucci Yes
leigh Yes
levim Yes
lstrojny Yes
malukenho Yes
mbeccati Yes
nikic Yes
pauloelr Yes
ramsey Yes
rdohms Yes
rmf Yes
santiagolizardo Yes
seld Yes
stas Yes
stelianm Yes
subjective Yes
till Yes
timo Yes
tyrael Yes
yunosh Yes
zeev Yes