PHP Boolean

Summary: in this tutorial, you’ll learn about the PHP Boolean data type and the boolean values

Introduction to PHP Boolean

A boolean value represents a truth value. In other words, a boolean value can be either true or false. PHP uses the bool type to represent boolean values.

To represent boolean literals, you can use the true and false keywords. These keywords are case-insensitive. Therefore, the following are the same as true:

• True
• TRUE

And the following are the same as false:

• False
• FALSE

When you use non-boolean values in a boolean context, e.g., if statement. PHP evaluates that value to a boolean value. The following values evaluate to false:

• The keyword false
• The integer zero (0)
• The floating-point number zero (0.0)
• The empty string ('') and the string "0"
• The NULL value
• An empty array, i.e., an array with zero elements

PHP evaluates other values to true.

The following shows how to declare variables that hold Boolean values:

$is_submitted = false;
$is_valid = true;Code language: PHP (php)

To check if a value is a Boolean, you can use the built-in function is_bool(). For example:

$is_email_valid = false;
echo is_bool($is_email_valid);Code language: PHP (php)

When you use the echo to show a boolean value, it’ll show 1 for true and nothing for false, which is not intuitive. To make it more obvious, you can use the var_dump() function. For example:

<?php

$is_email_valid = false;
var_dump($is_email_valid);

$is_submitted = true;
var_dump($is_submitted);Code language: HTML, XML (xml)

Output:

bool(false)
bool(true) Code language: JavaScript (javascript)

Summary

• A boolean value represents a truth value, which is either true or false.
• PHP evaluates the following values to false: false, 0, 0.0, empty string (“”), “0”, NULL, an empty array; other values are true.