PHP Data Types

Variables can store data of different types, and different data types can do different things. PHP supports several data types that allow you to work with text, numbers, logic, and complex collections of data.

The var_dump() Function

Before we dive into types, you must know about var_dump(). It is a built-in PHP function that returns the data type and value of a variable. It is the most useful tool for debugging and learning data types.

<?php
    $x = 5;
    var_dump($x); // Outputs: int(5)
?>

Supported PHP Data Types

PHP supports the following primary data types:

1. 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.

<?php
    $x = "Hello world!";
    $y = 'Hello world!';
?>

2. Integer

An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647. An integer must have at least one digit and cannot contain commas or blanks.

<?php
    $x = 5985;
    var_dump($x);
?>

3. Float (Floating Point Numbers)

A float (floating point number) is a number with a decimal point or a number in exponential form. In some documentation, it is also referred to as a double.

<?php
    $x = 10.365;
    var_dump($x);
?>

4. Boolean

A Boolean represents two possible states: TRUE or FALSE. Booleans are often used in conditional testing.

<?php
    $x = true;
    $y = false;
?>

5. Array

An array stores multiple values in one single variable. It is a collection of data, and can store values of different types within the same array.

<?php
    $cars = array("Volvo", "BMW", "Toyota");
    var_dump($cars);
?>

6. Object

Classes and objects are the two main aspects of object-oriented programming. An object is a data type which stores data and information on how to process that data with methods.

<?php
    class Car {
        public $color;
        public $model;
        public function __construct($color, $model) {
            $this->color = $color;
            $this->model = $model;
        }
    }
    $myCar = new Car("black", "Volvo");
    var_dump($myCar);
?>

7. 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.

<?php
    $x = "Hello world!";
    $x = null; // $x is now NULL
    var_dump($x);
?>

Key Points to Remember

• Use var_dump() to see the data type and value of any variable.
• Strings must be wrapped in quotes.
• Integers are whole numbers, while Floats are decimal numbers.
• Arrays can store multiple values in a single variable.
• NULL serves as a placeholder for a variable with no value.
• PHP is loosely typed, so a variable can change its data type depending on the value it currently holds.

Common Mistakes to Avoid

Try It: Comparing var_dump() Output

Run this to see exactly how PHP reports each type — useful whenever a bug turns out to be a type mismatch:

<?php
    var_dump("5");     // string(1) "5"
    var_dump(5);       // int(5)
    var_dump("5" == 5); // bool(true)  -- loose comparison
    var_dump("5" === 5); // bool(false) -- strict comparison
?>

Frequently Asked Questions