Here is the list of PHP reserved words and usual constants.
and.
break.
case.
class.
continue.
default.
do.
else.
elseif.
empty().
endfor.
endif.
endswitch.
endwhile.
E_ALL.
E_PARSE.
E_ERROR.
E_WARNING.
extends.
FALSE.
for.
foreach.
function.
if.
include().
include_once().
global.
list().
new.
not.
or.
PHP_OS.
PHP_VERSION.
require().
require_once().
return.
static.
switch.
this.
TRUE.
var.
xor.
virtual().
while.
__FILE__.
__LINE__.