PHP 变量与数组

$v=	NULL	0	FALSE	""	TRUE	1	1.3	-1	"-1"	-1.7	"1"	"1.3"	"0"	" "	"string"	"123str"	"str123"	array()	array(1)	unset($v)
isset($v)	false	true	true	true	true	true	true	true	true	true	true	true	true	true	true	true	true	true	true	false
if ($v) {	false	false	false	false	true	true	true	true	true	true	true	true	false	true	true	true	true	false	true	false
empty($v)	true	true	true	true	false	false	false	false	false	false	false	false	true	false	false	false	false	true	false	true
is_scalar($v)	false	true	true	true	true	true	true	true	true	true	true	true	true	true	true	true	true	false	false	false
is_bool($v)	false	false	true	false	true	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false
is_string($v)	false	false	false	true	false	false	false	false	true	false	true	true	true	true	true	true	true	false	false	false
is_int($v)	false	true	false	false	false	true	false	true	false	false	false	false	false	false	false	false	false	false	false	false
is_numeric($v)	false	true	false	false	false	true	true	true	true	true	true	true	true	false	false	false	false	false	false	false
is_float($v)	false	false	false	false	false	false	true	false	false	true	false	false	false	false	false	false	false	false	false	false
is_null($v)	true	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	true
is_array($v)	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	false	true	true	false
ctype_digit($v)	false	false	false	false	false	false	false	false	false	false	true	false	true	false	false	false	false	false	false	false
ctype_alnum($v)	false	false	false	false	false	false	false	false	false	false	true	false	true	false	true	true	true	false	false	false
ctype_lower($v)	false	false	false	false	false	false	false	false	false	false	false	false	false	false	true	false	false	false	false	false
ctype_print($v)	false	false	false	false	false	false	false	false	true	false	true	true	true	true	true	true	true	false	false	false
ctype_space($v)	false	false	false	false	false	false	false	false	false	false	false	false	false	true	false	false	false	false	false	false
ctype_cntrl($v)	false	true	false	false	false	true	false	false	false	false	false	false	false	false	false	false	false	false	false	false
ctype_graph($v)	false	false	false	false	false	false	false	false	true	false	true	true	true	false	true	true	true	false	false	false
$v=	NULL	0	FALSE	""	TRUE	1	1.3	-1	"-1"	-1.7	"1"	"1.3"	"0"	" "	"string"	"123str"	"str123"	array()	array(1)	unset($v)
count($v)	0	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	0	1	0
gettype($v)	NULL	integer	boolean	string	boolean	integer	double	integer	string	double	string	string	string	string	string	string	string	array	array	NULL
intval($v)	0	0	0	0	1	1	1	-1	-1	-1	1	1	0	0	0	123	0	0	1	0
floatval($v)	0	0	0	0	1	1	1.3	-1	-1	-1.7	1	1.3	0	0	0	123	0	0	1	0
strlen($v) NEW!	0	1	0	0	1	1	3	2	2	4	1	3	1	1	6	6	6	5	5	0
strval($v)	''	'0'	''	''	'1'	'1'	'1.3'	'-1'	'-1'	'-1.7'	'1'	'1.3'	'0'	' '	'string'	'123str'	'str123'	'Array'	'Array'	''
floor($v)	0	0	0	0	1	1	1	-1	-1	-2	1	1	0	0	0	123	0	false	false	0
ceil($v)	0	0	0	0	1	1	2	-1	-1	-1	1	2	0	0	0	123	0	false	false	0
round($v)	0	0	0	0	1	1	1	-1	-1	-2	1	1	0	0	0	123	0	false	false	0
$v=	NULL	0	FALSE	""	TRUE	1	1.3	-1	"-1"	-1.7	"1"	"1.3"	"0"	" "	"string"	"123str"	"str123"	array()	array(1)	unset($v)

$arr = array (
  'zero' => 0,
  'one' => 1,

  'three' => 'Three',
  'null' => NULL,
  'false' => false,
  'empty' => '',
);   

$key =	'zero'	'one'	'two'	'three'	'null'	'false'	'empty'
isset($arr[$key])	true	true	false	true	false	true	true
array_key_exists($key,$arr)	true	true	false	true	true	true	true
if ($arr[$key]) {	false	true	false	true	false	false	false
empty($arr[$key])	true	false	true	false	true	true	true
gettype($arr[$key])	integer	integer	NULL	string	NULL	boolean	string

In case interested all these tests are carried out live as this page is rendered (with a bit of 'eval'), so any upgrade of PHP will immediately showup. If you have a different version of PHP, and would like to host a copy then let me know at the link below.