Values & Types

Type hierarchy

PHP’s type hierarchy

Literal Types

Category Types Values
Special Null (doc) null
Scalar Boolean (doc) true
false, False, FALSE
Scalar Integer (doc) -15
15, 0b1111, 0o17, 0xf
Scalar Float (doc) -1234.5
1234.5, 1.2345e3
0.0012, 1.2E-3
Scalar String (doc) 'Hello'
"Hello"
Compound Array (doc) []
[1, 2, 3]
[1, '2', true]
['name' => 'Alice', 'email' => 'alice@ifpb.edu']
Compound Object (doc) stdObject
PDO

Pseudo-types: mixed, number, callback, void

Type Casting

echo (int) 1.5;  //=> 1
echo (int) "";   //=> 0
echo (int) true; //=> 1

PHP type comparison tables

Expression gettype() empty() is_null() isset() boolean : if($x)
$x = ""; string TRUE FALSE TRUE FALSE
$x = null; NULL TRUE TRUE FALSE FALSE
var $x; NULL TRUE TRUE FALSE FALSE
$x is undefined NULL TRUE TRUE FALSE FALSE
$x = array(); array TRUE FALSE TRUE FALSE
$x = array('a', 'b'); array FALSE FALSE TRUE TRUE
$x = false; boolean TRUE FALSE TRUE FALSE
$x = true; boolean FALSE FALSE TRUE TRUE
$x = 1; integer FALSE FALSE TRUE TRUE
$x = 42; integer FALSE FALSE TRUE TRUE
$x = 0; integer TRUE FALSE TRUE FALSE
$x = -1; integer FALSE FALSE TRUE TRUE
$x = "1"; string FALSE FALSE TRUE TRUE
$x = "0"; string TRUE FALSE TRUE FALSE
$x = "-1"; string FALSE FALSE TRUE TRUE
$x = "php"; string FALSE FALSE TRUE TRUE
$x = "true"; string FALSE FALSE TRUE TRUE
$x = "false"; string FALSE FALSE TRUE TRUE