Data Types in PHP

PHP supports eight primitive types.

Four scalar types:

boolean

integer

float (floating-point number, aka 'double')

string

Two compound types:

array

object

And finally two special types:

resource

NULL

This page also introduces some pseudo-types for readability reasons:

mixed

number

callback

And the pseudo-variable $....

You may also find some references to the type "double". Consider double the same as float, the two names exist only for historic reasons.

The type of a variable is usually not set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used.

Note: If you want to check out the type and value of a certain expression, use var_dump().

If you simply want a human-readable representation of the type for debugging, use gettype(). To check for a certain type, do not use gettype(), but use the is_type functions. Some examples:

$a_bool = TRUE; // a boolean

$a_str = "foo"; // a string

$a_str2 = 'foo'; // a string

$an_int = 12; // an integer

echo gettype($a_bool); // prints out: boolean

echo gettype($a_str); // prints out: string

// If this is an integer, increment it by four

if (is_int($an_int)) {

$an_int += 4;

}

// If $bool is a string, print it out

// (does not print out anything)

if (is_string($a_bool)) {

echo "String: $a_bool";

}

?>

If you would like to force a variable to be converted to a certain type, you may either cast the variable or use the settype() function on it.