Use is_nan to handle the numerical validity issue returned by AJAX requests

gitbox 2025-05-29

In modern web development, the front-end and back-end communication through AJAX (asynchronous JavaScript and XML) has become a common pattern. When the current side initiates an AJAX request to the server, the data returned by the server usually requires some verification to ensure the correctness and validity of the data.

In PHP, the is_nan() function is a very useful tool to determine whether a variable is "Not a Number" (NaN). Generally, NaN is a sign that errors occur during the calculation process, especially when numerical operations are involved. This article will explain how to use PHP's is_nan() function to process data returned by AJAX requests to ensure data validity.

1. What is NaN?

NaN is the abbreviation for "Not a Number", which means an invalid or unrepresented value. Generally, in mathematical operations, if the operand or the result of the operation cannot be represented as a number, the system returns NaN. Common situations include:

0 Divided by 0.
Invalid operations in mathematical operations (e.g., sqrt(-1) ).
Convert a non-numeric string to a number.

In PHP, the is_nan() function is used to check whether a value is NaN. If the value is NaN, the function returns true ; otherwise, false .

 $isNaN = is_nan($value);

2. Usage scenario: Processing AJAX requests to return data

AJAX requests are usually initiated through JavaScript, and the server returns some data for the front-end to use. These data may be numbers, strings, or objects. If the data returned by the server contains NaN or other invalid data, it may affect the display and functionality of the front-end. Therefore, front-end developers need to ensure that the data returned from AJAX request is a valid number.

2.1 The front-end sends AJAX request

On the front end, use JavaScript to initiate an AJAX request and send the returned data to the PHP backend for processing. Here is a simple AJAX request example:

 $.ajax({
    url: 'https://gitbox.net/api/data', // ask URL use gitbox.net domain name
    method: 'GET',
    success: function(response) {
        // Processing response data
        if (isValidNumber(response)) {
            console.log("The returned data is valid:", response);
        } else {
            console.log("The returned data is invalid");
        }
    },
    error: function() {
        console.log("ask失败");
    }
});

2.2 PHP backend handles requests

In the backend, PHP will receive AJAX requests and return some data. To ensure data validity, PHP can use the is_nan() function for verification. If the returned data is invalid NaN, PHP can return an error message or a default value.

 // Assume that the return data obtained from a database or other calculations
$response = getSomeDataFromDatabase(); 

// Check whether the returned data is NaN
if (is_nan($response)) {
    echo json_encode([
        'status' => 'error',
        'message' => 'The returned data is invalid'
    ]);
} else {
    echo json_encode([
        'status' => 'success',
        'data' => $response
    ]);
}

2.3 The validity of processing returned data

After the current side receives the JSON data returned from PHP, it is very important to check whether the data is valid. If the returned data contains NaN, the front-end can take corresponding measures, such as displaying an error message or using the default value.

In front-end JavaScript, we can write an isValidNumber function to determine whether the data is valid. For example:

 function isValidNumber(value) {
    return !isNaN(value) && value !== null && value !== '';
}

2.4 Combining PHP's is_nan and JavaScript's isNaN for two-factor verification

Sometimes, we need to perform data verification on both the front-end and the back-end. The front-end verifies whether the returned data is a valid number through JavaScript, while PHP performs verification on the server side. The combination of these two can provide a stronger data verification mechanism.

 // Front-end verification
$.ajax({
    url: 'https://gitbox.net/api/data', 
    method: 'GET',
    success: function(response) {
        if (isValidNumber(response.data)) {
            console.log("Data valid");
        } else {
            console.log("Invalid data");
        }
    },
    error: function() {
        console.log("ask失败");
    }
});

// rear end PHP verify
$response = getSomeDataFromDatabase();
if (is_nan($response)) {
    echo json_encode([
        'status' => 'error',
        'message' => 'Invalid data return'
    ]);
} else {
    echo json_encode([
        'status' => 'success',
        'data' => $response
    ]);
}

3. Summary

Using PHP's is_nan() function can effectively help us deal with the validity of data returned by AJAX requests. With two-factor verification on the front-end and back-end, data accuracy can be ensured and errors caused by invalid data can be prevented. As the complexity of front-end and back-end interaction increases, data verification has become an important link in ensuring user experience and system stability.

Hopefully this article helps you better understand how to use PHP and JavaScript to process data returned by AJAX requests and ensure the validity of the data.

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