PHP保留关键词
__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	for	 foreach  function	
global	goto	if	implements  include 	include_once	
instanceof	insteadof	interface  isset()	 list()	
match	namespace	new
or	print	private	 protected	public
require	 require_once	return	
static	switch
throw	trait	try	unset()	use
var	while	xor 	yield	yield from