Uppercase Booleans vs. Lowercase in PHP
language-history, php
Solution
The official PHP manual says:
To specify a bool literal, use the constants true or false. Both are case-insensitive.
So yeah, `true === TRUE` and `false === FALSE`.
Personally, however, I prefer `TRUE` over `true` and `FALSE` over `false` for readability reasons. It's the same reason for my preference on using `OR` over `or` or `||`, and on using `AND` over `and` or `&&`.
The PSR-2 standard requires `true`, `false` and `null` to be in lower case.
Problem
When I was learning PHP, I read somewhere that you should always use the upper case versions of booleans, `TRUE` and `FALSE`, because the "normal" lowercase versions, `true` and `false`, weren't "safe" to use. It's now been many years, and every PHP script I've written uses the uppercase version. Now, though, I am questioning that, as I have seen plenty of PHP written with the lowercase version (i.e. Zend Framework). Is/Was there ever a reason to use the uppercase version, or is it perfectly OK to use the lowercase? edit: Forgot to mention that this applies to `NULL` and `null` as well.