PHP Data Types

PHP Data Types

Variables can store data of different types, and different data types can do different things.

PHP supports the following data types:

• string (text values)
• int (whole numbers)
• float (decimal numbers)
• bool (true or false)
• array (multiple values)
• object (stores data as objects)
• null (empty variable)
• resource (references external resources)

Use var_dump() to Get the Data Type

To get the data type and the value of a variable, use the var_dump() function.

$x = 5;
var_dump($x); // dumps int(5)

PHP String Data Type

A string is a sequence of characters, like "Hello world!".

$x = 'Hello world!';
var_dump($x);

PHP Int Data Type

An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.

Rules for integers:

• An integer must have at least one digit
• An integer must not have a decimal point
• An integer can be either positive or negative
• Integers can be specified in: decimal (base 10), hexadecimal (base 16), octal (base 8), or binary (base 2) notation

$x = 5985;
var_dump($x);

PHP Float Data Type

A float (floating point number) is a number with a decimal point or a number in exponential form.

$x = 10.365;
var_dump($x);

PHP Bool Data Type

A Boolean data type represents two possible states: TRUE or FALSE.

$x = true;
var_dump($x);

Booleans are often used in conditional testing.

You will learn more about conditional testing in the PHP If...Else chapter.

PHP Array Data Type

An array data type stores multiple values in one single variable.

In the following example $cars is an array:

$cars = array("Volvo","BMW","Toyota");
var_dump($cars);

You will learn more about arrays later in this tutorial.

PHP Object Data Type

An object data type holds an instance of a programmer-defined class.

class Car {
  public $color;
  public $model;
  public function __construct($color, $model) {
    $this->color = $color;
    $this->model = $model;
  }
  public function message() {
    return "My car is a " . $this->color . " " . $this->model . "!";
  }
}

$myCar = new Car("red", "Volvo");
var_dump($myCar);

Do not worry if you do not understand the PHP Object syntax, you will learn more about that in the PHP Classes/Objects chapter.

PHP NULL Data Type

Null is a special data type which can have only one value: NULL.

A variable of data type NULL is a variable that has no value assigned to it.

Tip: If a variable is created without a value, it is automatically assigned a value of NULL.

Variables can also be emptied by setting the value to NULL:

$x = "Hello world!";
$x = null;
var_dump($x);

Changing Data Type

If you assign an integer value to a variable, the data type will automatically be an integer.

If you assign a string to the same variable, the data type will change to a string:

$x = 5;
var_dump($x);

$x = "Hello";
var_dump($x);

If you want to change the data type of an existing variable, but not by changing the value, you can use casting.

Casting allows you to change data type on variables:

$x = 5;
$x = (string) $x;
var_dump($x);

You will learn more about casting in the PHP Casting Chapter.

PHP Resource Data Type

The special resource data type is not an actual data type. It holds a reference to an external resource, such as a database connection or a file handler.

We will not talk about the resource data type here, since it is an advanced topic.