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I have a javascript file that captures form input, makes an XMLHTTP POST request with the input, and handles errors. I am currently POSTing to a separate PHP file, as the request requires sensitive API data and needs encoding. From the PHP file, I then send a cURL request to post the form input to the remote URL.

I want to handle errors based on the cURL response, but the XHR errors are different and take precedent over the cURL errors. Are both these requests necessary, or should I only be making either a single XHR or cURL request?

rachel wagschal
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1 Answers1

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Whether or not both requests are necessary depends on your use case. Since yours sounds as they are indeed necessary, there's absolutely nothing wrong with it.

How you handle server-side errors client-side is also entirely up to you. For example, let's assume this pretty basic XHR handler, which sends some JSON data off to some endpoint and evaluates the response:

var xhr = new XMLHttpRequest();

xhr.open('POST', '/endpoint.php');
xhr.setRequestHeader('Content-Type', 'application/json');

xhr.onload = () => {

    const status   = xhr.status;
    const response = JSON.parse(xhr.responseText);
    
    if (status == 200) {

        // Everything's fine
        console.log(response.data);

    } else {

        // Some error occured
        console.log(status, response.data);
    }
};

xhr.send(JSON.stringify({}));

index.html

The above error handling strategy revolves around the HTTP status code received from the server, so we'll need to make sure they're send according to our needs:

/**
 * In case an error occurred, send an error response.
 */ 
function error(string $message) {

    // For properly returning a JSON response, see:
    // https://stackoverflow.com/a/62834046/3323348
    header("Content-type: application/json; charset=utf-8");
    http_response_code(400); // HTTP status code - set to whatever code's appropriate

    echo json_encode(['data' => $message]);
}

/**
 * Send a response denoting a success.
 */ 
function success(array $data) {

    // For properly returning a JSON response, see:
    // https://stackoverflow.com/a/62834046/3323348
    header("Content-type: application/json; charset=utf-8");
    http_response_code(200);

    echo json_encode(['data' => $data]);
}

// For proper error checking on JSON data, see:
// https://stackoverflow.com/a/37847337/3323348
$data = json_decode(file_get_contents('php://input'), true);

// Assume some processing happened. That result is either
// a success, or an error.
$success = mt_rand(0,1);
$success ? success($data) : error('An error occured.');

endpoint.php

Regarding cURL, you could easily change the last two lines to e.g.:

if(curl_errno($ch)) { // Assuming $ch is your cURL handle

    error('Curl error: '.curl_error($ch));
}
else {

    success($data);
}

Or you adapt the error function - if it would accept an array instead of a simple string, you'd be able to return more complex error data to your JavaScript client:

$curl_error = curl_errno($ch);

if ($curl_error) {

    error([

        'type' => 'cURL', 
        'no' => curl_errno($ch), 
        'message' => curl_error($ch)
    ]);
}

You don't have to stick with status codes for your error handling, though. You could send a JSON object back with one key denoting some successfully collected data, and one denoting an error if an error occurred. Or whatever suits your needs.

nosurs
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