PHP Manual: List of Keywords

List of Keywords

These words have special meaning in PHP. Some of them represent things which look like functions, some look like constants, and so on - but they're not, really: they are language constructs. The following words cannot be used as constants, class names, or function names. They are, however, allowed as property, constant, and method names of classes, interfaces, traits and enums, except that class may not be used as constant name.

**PHP Keywords**
__halt_compiler()	abstract	and	array()	as
break	callable	case	catch	class
clone	const	continue	declare	default
die()	do	echo	else	elseif
empty()	enddeclare	endfor	endforeach	endif
endswitch	endwhile	eval()	exit()	extends
final	finally	fn (as of PHP 7.4)	for	foreach
function	global	goto	if	implements
include	include_once	instanceof	insteadof	interface
isset()	list()	match (as of PHP 8.0)	namespace	new
or	print	private	protected	public
readonly (as of PHP 8.1.0) *	require	require_once	return	static
switch	throw	trait	try	unset()
use	var	while	xor	yield
yield from

* readonly may be used as function name.

**Compile-time constants**
__CLASS__	__DIR__	__FILE__	__FUNCTION__	__LINE__
__METHOD__	__PROPERTY__	__NAMESPACE__	__TRAIT__