PHP comparison results

Boolean results of PHP operations commonly used when comparing with PHP's if.

Always try to use strict comparison (three equal signs ===) to avoid ambiguity. See also: the if command and PHP type comparison tables on php.net.

Ambiguous (avoid)

$value =>	undefined	null	false	true	"0"	0	"1"	1	empty string ""	"string"	array()	array("foo")
$value == null	true	true	true	false	false	true	false	false	true	false	true	false
$value == false	true	true	true	false	true	true	false	false	true	false	true	false
!$value	true	true	true	false	true	true	false	false	true	false	true	false
empty($value)	true	true	true	false	true	true	false	false	true	false	true	false
$value == 0	true	true	true	false	true	true	false	false	true	true	false	false
$value == "0"	false	false	true	false	true	true	false	false	false	false	false	false
$value == true	false	false	false	true	false	false	true	true	false	true	false	true
$value == 1	false	false	false	true	false	false	true	true	false	false	false	false
$value == "1"	false	false	false	true	false	false	true	true	false	false	false	false

$value =>	undefined	null	false	true	"0"	0	"1"	1	empty string ""	"string"	array()	array("foo")
isset($value)	false	false	true	true	true	true	true	true	true	true	true	true
is_null($value)	true	true	false	false	false	false	false	false	false	false	false	false
$value === null	true	true	false	false	false	false	false	false	false	false	false	false
$value === false	false	false	true	false	false	false	false	false	false	false	false	false
$value === true	false	false	false	true	false	false	false	false	false	false	false	false
$value === "0"	false	false	false	false	true	false	false	false	false	false	false	false
$value === 0	false	false	false	false	false	true	false	false	false	false	false	false
$value === "1"	false	false	false	false	false	false	true	false	false	false	false	false
$value === 1	false	false	false	false	false	false	false	true	false	false	false	false

$value =>	undefined	null	false	true	"0"	0	"1"	1	empty string ""	"string"	array()	array("foo")
empty($value)	true	true	true	false	true	true	false	false	true	false	true	false
$value == false	true	true	true	false	true	true	false	false	true	false	true	false

If a $value is undefined $value == FALSE will throw you a warning:

Notice: Undefined variable: value in /yourscript.php on line 1

empty($value) will not.