# Is_nan()

Today, we will discuss the `is_nan()` function in PHP. This function is used to determine whether a value is not a number (NaN).

## What is the is_nan() Function?

The `is_nan()` function in PHP is a built-in function that is used to determine whether a value is not a number (NaN). NaN is a value that represents an undefined or unrepresentable result of a mathematical operation, such as the result of dividing zero by zero. The `is_nan()` function takes a value as input and returns true if the value is NaN, and false otherwise.

## How to Use the is_nan() Function

Using the `is_nan()` function in PHP is very simple. Here is an example of how to use the function:

``````<?php
\$number = acos(1.5);

// Check if the number is NaN using the is_nan() function
if (is_nan(\$number)) {
echo "The number is not a number";
} else {
echo "The number is a number";
}
?>``````

In this example, we set a variable to the result of the `acos()` function with a value of 1.5 as input. Since the `acos()` function is undefined for values greater than 1, the result is NaN. We then call the `is_nan()` function with the variable as a parameter to check if it is NaN. Finally, we output a message to the screen based on whether the number is NaN or not.

## Conclusion

The `is_nan()` function in PHP is a useful tool for any PHP developer working with numbers. By using this function, you can determine whether a value is NaN or not, which can be useful in a variety of applications. We hope that this guide has been helpful in understanding how to use the `is_nan()` function in your PHP code.