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Variables can store data of different types, and different data types can do different things
Variables can store data of different types, and different data types can do different things.
PHP supports the following data types:
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:
<?php
$x = "Hello world!";
$y = 'Hello world!';
echo $x;
echo "<br>";
echo $y;
?>
An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.
Rules for integers:
In the following example $x is an integer. The PHP var_dump() function returns the data type and value:
<?php
$x = 5985;
var_dump($x);
?>
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:
<?php
$x = 10.365;
var_dump($x);
?>
A Boolean represents two possible states: TRUE or FALSE.
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.
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:
<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>
You will learn a lot more about arrays in later chapters of this tutorial.
Classes and objects are the two main aspects of object-oriented programming.
A class is a template for objects, and an object is an instance of a class.
When the individual objects are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties.
Let's assume we have a class named Car. A Car can have properties like model, color, etc. We can define variables like $model, $color, and so on, to hold the values of these properties.
When the individual objects (Volvo, BMW, Toyota, etc.) are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties.
If you create a __construct() function, PHP will automatically call this function when you create an object from a class.
<?php
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("black", "Volvo");
echo $myCar -> message();
echo "<br>";
$myCar
= new Car("red", "Toyota");
echo $myCar -> message();
?>
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.
Variables can also be emptied by setting the value to NULL:
<?php
$x = "Hello world!";
$x = null;
var_dump($x);
?>
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.