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:

$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.


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.

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