false, null and true must be recognized as constants in PHP

[ghost]

null is not a keyword

null is a case­‑insensitive predefined constant (see https://secure.php.net/manual/en/reserved.constants.php).

<?php
echo (defined('NULL') && defined('null')) ? 'Defined' : 'Not defined';
// Prints “Defined”

As can be seen in the table below, misplaced null causes a compile error, whereas keywords (or language constructs) cause parse errors.

Naming	with any keyword	with null
class	E_PARSE	E_COMPILE_ERROR
constant	E_PARSE ⁠*	E_NOTICE
function	E_PARSE	✔️
method	✔️	✔️
namespace	E_PARSE	✔️
trait	E_PARSE	E_COMPILE_ERROR
variable	✔️	✔️

* ⁠Fails on the direct access, i. e., without constant().

So I think Prism should categorize null as a constant, not as a keyword. This is unlikely to adversely affect backward compatibility, because constant is also a well­‑known class, which is already supported by most of the themes.

false and true are also constants

false and true are also case­‑insensitive predefined constants and have all the same features that null has. Thus, they should get the same additional classes.

Solution

Remove null from the keyword regex. Add the following code:

Prism.languages.insertBefore('php', 'class-name', {
	'null': {
		pattern: /\b(?:null)\b/i,
		alias: 'constant predefined-constant'
	}
});

Redefine the boolean regex, which is inherited from clike:

Prism.languages.insertBefore('php', 'class-name', {
	'boolean': {
		pattern: /\b(?:true|false)\b/i,
		alias: 'constant predefined-constant'
	}
});

Expected results

false and true

Result	CSS classes
Current	token boolean
Expected	token boolean constant predefined-constant

null

Result	CSS classes
Current	token keyword
Expected	token null constant predefined-constant