Variables can store data of different types, and different data types can do different things.PHP supports the following data types:
- String
- Integer
- Float (floating point numbers - also called double)
- Boolean
- Array
- Object
- NULL
- Resource
PHP String
A string is a sequence of characters, like "Hello world!".
A string can be any text inside quotes. You can use single or double quotes:
<!DOCTYPE html>
<html>
<body>
<?php
$x = "Hello world!";
$y = 'Hello world!';
echo $x;
echo "<br>";
echo $y;
?>
</body>
</html>
<html>
<body>
<?php
$x = "Hello world!";
$y = 'Hello world!';
echo $x;
echo "<br>";
echo $y;
?>
</body>
</html>
PHP Integer
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 three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0)
In the following example $x is an integer. The PHP var_dump() function returns the data type and value:
<!DOCTYPE html>
<html>
<body>
<?php
$x = 5985;
var_dump($x);
?>
</body>
</html>
<html>
<body>
<?php
$x = 5985;
var_dump($x);
?>
</body>
</html>
PHP Float
A float (floating point number) is a number with a decimal point or a number in exponential form.
In the following example $x is a float. The PHP var_dump() function returns the data type and value:
<!DOCTYPE html>
<html>
<body>
<?php
$x = 10.365;
var_dump($x);
?>
</body>
</html>
<html>
<body>
<?php
$x = 10.365;
var_dump($x);
?>
</body>
</html>
PHP Boolean
A Boolean represents two possible states: TRUE or FALSE.
$x = true;
$y = false;
$y = false;
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.
PHP Array
An array stores multiple values in one single variable.
In the following example $cars is an array. The PHP var_dump() function returns the data type and value:
<!DOCTYPE html>
<html>
<body>
<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>
</body>
</html>
<html>
<body>
<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>
</body>
</html>
You will learn a lot more about arrays in later chapters of this tutorial.
PHP Object
An object is a data type which stores data and information on how to process that data.
In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods:
<!DOCTYPE html>
<html>
<body>
<?php
class Car {
function Car() {
$this->model = "VW";
}
}
// create an object$herbie = new Car();
// show object propertiesecho $herbie->model;
?>
</body>
</html>
<html>
<body>
<?php
class Car {
function Car() {
$this->model = "VW";
}
}
// create an object$herbie = new Car();
// show object propertiesecho $herbie->model;
?>
</body>
</html>
You will learn more about objects in a later chapter of this tutorial.
PHP NULL Value
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:
You will learn more about objects in a later chapter of this tutorial.
PHP NULL Value
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:
PHP Resource
The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP.
A common example of using the resource data type is a database call.
We will not talk about the resource type here, since it is an advanced topic.
