PHP Variable Handling is_bool() Function

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The PHP Variable Handling is_bool() function is used to determine whether a variable is a boolean value. Boolean values are either true or false. This function determines if a variable's value is of the boolean type or not. It only requires one parameter, which is the variable you want to analyze.

If the variable is boolean, the function returns True. If the value is not a boolean, it returns false. This is useful when you want to confirm the type of a variable before executing an operation.

Syntax

Below is the syntax of the PHP Variable Handling is_bool() function −

bool is_bool (mixed $value )

Parameters

This function accepts $value parameter which is the variable to be evaluated.

Return Value

The is_bool() function returns TRUE if the value is a bool. Otherwise it returns FALSE.

PHP Version

First introduced in core PHP 4, the is_bool() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

This basic program implemented to check if the variable $value is a boolean or not. As the $value parameter is set to true, the PHP Variable Handling is_bool() function returns 1, showing that it is a boolean.

<?php
   $value = true;
   echo is_bool($value);
?>

Output

Here is the outcome of the following code −

1

Example 2

In the below PHP code we will use the is_bool() function and check a non boolean value to check that the function returns false ot not. So in our code the $number variable is an integer. As integers are not booleans so the is_bool() returns false.

<?php
   $number = 42;
   echo is_bool($number);
   echo "It is not a boolean value.";
?> 

Output

This will generate the below output −

It is not a boolean value.

Example 3

Now the below code checks that a given variable is a boolean value or not using the is_bool() in a conditional statement. So we will use the is_bool() inside an if statement. If the variable $value is a boolean, it prints "The variable is a boolean."

<?php
   $value = false;
   if (is_bool($value)) {
      echo "The variable is a boolean.";  
   } else {
      echo "The variable is not a boolean.";
   }
?> 

Output

This will create the below output −

The variable is a boolean.

Example 4

In the following example, we are using the is_bool() function to check three different variables. The first variable $var1 is a boolean, but $var2 and $var3 are not. So the output shows which variables are booleans and which are not.

<?php
   $var1 = true;
   $var2 = 100;
   $var3 = "Hello";

   echo is_bool($var1) ? "var1 is a boolean\n" : "var1 is not a boolean\n";  
   echo is_bool($var2) ? "var2 is a boolean\n" : "var2 is not a boolean\n";  
   echo is_bool($var3) ? "var3 is a boolean\n" : "var3 is not a boolean\n"; 
?> 

Output

Following is the output of the above code −

var1 is a boolean
var2 is not a boolean
var3 is not a boolean