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

abstract (as of PHP 5)	and	array()	as	break
case	catch (as of PHP 5)	cfunction (PHP 4 only)	class	clone (as of PHP 5)
const	continue	declare	default	do
else	elseif	enddeclare	endfor	endforeach
endif	endswitch	endwhile	extends	final (as of PHP 5)
for	foreach	function	global	goto (as of PHP 5.3)
if	implements (as of PHP 5)	interface (as of PHP 5)	instanceof (as of PHP 5)
namespace (as of PHP 5.3)	new	old_function (PHP 4 only)	or	private (as of PHP 5)
protected (as of PHP 5)	public (as of PHP 5)	static	switch	throw (as of PHP 5)
try (as of PHP 5)	use	var	while	xor

Compile-time constants

__CLASS__	__DIR__ (as of PHP 5.3)	__FILE__	__FUNCTION__	__METHOD__
__NAMESPACE__ (as of PHP 5.3)

Language constructs

die()	echo()	empty()	exit()	eval()
include()	include_once()	isset()	list()	require()
require_once()	return()	print()	unset()