Why are PHP booleans both lower case and upper case?

Question

Is there a difference between true and TRUE or false and FALSE in PHP?

Because you could have found this out yourself in five seconds with Google. — Interrobang, Dec 22 '11 at 03:11
Then what's up with this discussion: http://stackoverflow.com/questions/2013848/uppercase-booleans-vs-lowercase-in-php if all there is to this can be googled in 5 mins? — frnhr, Jun 19 '13 at 02:37

score 4 · Answer 1 · edited Jun 20 '20 at 09:12

If you intend to use JSON then the standard RFC7159 says :

The literal names MUST be lowercase. No other literal names are allowed.

And from Php 5.6 :

json_decode() now rejects non-lowercase variants of the JSON literals true, false and null at all times, as per the JSON specification

And according to PSR-2 standard :

PHP keywords MUST be in lower case.

The PHP constants true, false, and null MUST be in lower case.

Ps.: I could not post link to the RFC7159 because of SO limitations.

score 2 · Answer 2 · answered Dec 22 '11 at 03:39

Constants are case-sensitive per default. But for symmetry to the other identifier namespaces, they can be defined case-insensitively:

 define("mixedCASE", 123, TRUE);

 print MiXeDcAsE;

And that's just how TRUE and FALSE were pre-declared. (They aren't parser/language builtins.)

score 1 · Answer 3 · answered Dec 22 '11 at 02:58

1

Nope, the PHP Parser isn't very fussy when it comes to TRUE, true and FALSE, false

answered Dec 22 '11 at 02:58

Kodlee Yin

score 0 · Accepted Answer · answered Dec 22 '11 at 02:58

0

To specify a boolean literal, use the keywords TRUE or FALSE. Both are case-insensitive.

answered Dec 22 '11 at 02:58

Interrobang

4 Answers4