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. You cannot use any of the following words as constants, class names, function or method names. Using them as variable names is generally OK, but could lead to confusion.

**PHP Keywords**
__halt_compiler	abstract	and	array	as
break	callable (as of PHP 5.4)	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 (as of PHP 5.5)	for	foreach	function
global	goto (as of PHP 5.3)	if	implements	include
include_once	instanceof	insteadof (as of PHP 5.4)	interface	isset
list	namespace (as of PHP 5.3)	new	or	print
private	protected	public	require	require_once
return	static	switch	throw	trait (as of PHP 5.4)
try	unset	use	var	while
xor	yield (as of PHP 5.5)

**Compile-time constants**
__CLASS__	__DIR__ (as of PHP 5.3)	__FILE__	__FUNCTION__	__LINE__	__METHOD__
__NAMESPACE__ (as of PHP 5.3)	__TRAIT__ (as of PHP 5.4)