Use is_nan to determine whether the floating data transmitted by the front-end is legal

gitbox 2025-05-27

In web development, data transfer between front-end and back-end is very common, especially when the data types are relatively complex, how to ensure the legitimacy of the data has become an important issue in development. Especially for floating data types (such as floating point numbers), if there is no reasonable check, it may lead to some unexpected errors or inaccurate calculation results.

In PHP, the is_nan() function is a very useful tool to check whether a variable is "NaN" (Not a Number). "NaN" refers to a value that cannot be represented as a number, which usually occurs in numerical operations, such as: 0/0 or Math.sqrt(-1), etc.

Below we will explore in-depth how to use the is_nan() function to determine whether the floating data passed by the front-end is legal.

1. What is NaN (Not a Number)?

NaN is a special value in programming languages such as JavaScript and PHP, indicating that a calculation result is invalid or undeterminable. Common scenarios include:

The mathematical operation results are illegal, such as 0 / 0 .
Invalid floating numerical operations, such as sqrt(-1) .

The is_nan() function in PHP is used to detect whether a value is NaN.

2. Introduction to is_nan() function in PHP

PHP provides a built-in function is_nan() to determine whether a value is NaN. This function is used as follows:

 is_nan($var);

$var is the variable you need to check.
If the value of $var is NaN, is_nan() will return true , otherwise false .

3. How to determine whether the floating data transmitted by the front-end is legal?

In a web application, the front-end sends data to the back-end via form or AJAX request. Assuming you need to handle floating data passed by the front end, first you need to verify that the data is legal and make sure they are valid numbers.

The steps are as follows:

Receive data : When the front end passes floating data, the data is usually sent to the PHP backend via GET or POST requests. For example:

 $floatData = $_POST['floatData'];  // Receive data from front-end form

Verify data : Use is_nan() to check whether the received data is NaN. If it is NaN, it means that the data is invalid.

 if (is_nan($floatData)) {
    echo "The passed data is invalid（NaN）。Please check the input。";
} else {
    echo "The passed data is legal：".$floatData;
}

Processing data : If the data is valid, you can continue to perform calculations, storage, or other business operations. If the data is invalid, an error message is usually returned, requiring the front-end user to re-enter.

4. Complete example

Suppose you need to process a front-end passable floating data and verify that it is legal. Here is a complete PHP example that demonstrates how to use is_nan() to determine whether the data is legal:

 <?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Receive floating data transmitted by the front end
    $floatData = $_POST['floatData'];

    // Check if the data is NaN
    if (is_nan($floatData)) {
        echo "The passed data is invalid（NaN）。Please check the input。";
    } else {
        // If the data is legal，Carry out the next step
        echo "The passed data is legal：".$floatData;
    }
}
?>

<form method="POST" action="http://gitbox.net/processData.php">
    <label for="floatData">Please enter floating data：</label>
    <input type="text" name="floatData" id="floatData" />
    <input type="submit" value="submit" />
</form>

In this example, we use $_POST['floatData'] to get the floating data passed by the front end and judge whether it is NaN through is_nan() . If it is NaN, the user is prompted to enter invalid data; if the data is legal, the floating data is output.

5. Why do you need to check NaN?

Determining whether the data is NaN is an effective defensive programming practice. When processing user input, we cannot rely solely on front-end data type checking, especially in numerical calculations, where NaN values can lead to unpredictable results and even destroy the logic of the entire program. Therefore, verifying the legitimacy of data on the backend is an important step in ensuring application robustness.

6. Summary

The is_nan() function provides a convenient way to check whether there is an illegal NaN value in PHP. By combining front-end and back-end verification, we can ensure the legitimacy of the data and avoid incorrect calculation and data processing problems.

is_nan