PHP Data Types
Summary: in this tutorial, you will learn about PHP data types including scalar types, compound types, and special types.
Introduction to PHP data types
A type specifies the amount of memory that allocates to a value associated with it. A type also determines the operations that you can perform on it.
PHP has ten primitive types including four scala types, four compound types, and two special types:
Scalar types
- bool
- int
- float
- string
Compound types
- array
- object
- callable
- iterable
Special types
- resource
- null
Scalar types
A variable is a scalar when it holds a single value of the type integer, float, string, or boolean.
Integer
Integers are whole numbers defined in the set {…-3,-2-,-1,0,1,2,3…}. The size of the integer depends on the platform where PHP runs.
The constant PHP_INT_SIZE
specifies the size of the integer on a specific platform. PHP uses the int keyword to denote the integer type.
The following example illustrates some integers:
$count = 0;
$max = 1000;
$page_size = 10;
Code language: HTML, XML (xml)
Float
Floats are floating-point numbers, which are also known as floats, doubles, or real numbers.
PHP uses the IEEE 754 double format to represent floats. Like other programming languages, floats have limited precision.
PHP uses the float
keyword to represent the floating-point numbers. The following example illustrates the floating-point numbers in PHP:
$price = 10.25;
$tax = 0.08;
Code language: HTML, XML (xml)
Boolean
Boolean represents a truth value that can be either true
or false
. PHP uses the bool
keyword to represent the Boolean type.
The bool type has two values true
and false
. Since keywords are case-insensitive, you can use true
, True
, TRUE
, false
, False
, and False
to indicate boolean values.
The following example shows how to assign Boolean values to variables:
$is_admin = true;
$is_user_logged_in = false;
Code language: HTML, XML (xml)
When you use the values of other types in the boolean context, such as if-else and switch-case statements, PHP converts them to the boolean values.
PHP treats the following values as false
:
- The
false
keyword. - The integer 0 and -0 (zero).
- The floats 0.0 and -0.0 (zero).
- The empty string (
""
,''
) and the string “0”. - The empty array (
array()
or[]
). - The
null
. - The
SimpleXML
objects created from attributeless empty elements.
The values that are not one of these falsy values above are true
.
String
A string is a sequence of characters surrounded by single quotes (‘) or double quotes (“). For example:
$str = 'PHP scalar type';
$message = "PHP data types";
Code language: HTML, XML (xml)
Compound types
Compound data includes the values that contain more than one value. PHP has two compound types including array and object.
Array
An array is an ordered map that associates keys with values. For example, you can define a list of items in a shopping cart like this:
$carts = [ 'laptop', 'mouse', 'keyboard' ];
Code language: HTML, XML (xml)
The $carts
array contains three string values. It maps the index 0
, 1
, and 2
to the values 'laptop'
, 'mouse'
, and 'keyboard'
. The $carts
is called an indexed array because it uses numeric indexes as keys.
To access a value in an array, you use the square brackets:
echo $carts[0]; // 'laptop'
echo $carts[1]; // 'mouse'
echo $carts[2]; // 'keyboard'
Code language: HTML, XML (xml)
Besides numeric indexes, you can use strings as keys for the array elements. These arrays are known as associative arrays. For example:
$prices = [
'laptop' => 1000,
'mouse' => 50,
'keyboard' => 120
];
Code language: HTML, XML (xml)
To access an element in an associative array, you specify the key in the square brackets. For example:
echo $prices['laptop']; // 1000
echo $prices['mouse']; // 50
echo $prices['keyboard']; // 120
Code language: HTML, XML (xml)
Object
An object is an instance of a class. It’s a central concept in object-oriented programming.
An object has properties. For example, a person object may have the first name, last name, and age properties.
An object also has behaviors, which are known as methods. For example, a person object can have a method called getFullName()
that returns the full name.
To learn more about objects, check out the object tutorial.
Special types
PHP has two special types: null and resource
Null
The null
type has one value called null that represents a variable with no value.
Resource
The resource type holds a reference to an external resource, e.g. a filehandle or a database connection.
Summary
- PHP has four scalar types, four compound types, and two special types.
- Scale types: integer, float, string, and boolean.
- Compound types: array and object.
- Special types: null and resource.