Posting JSON Data with PHP cURL

In this tutorial, we will explore how to post JSON data using PHP’s cURL library. This is a common requirement when interacting with RESTful APIs or sending data to servers that expect JSON payloads.

Introduction to cURL

cURL (Client URL) is a PHP extension that allows you to transfer data specified with URLs. It supports various protocols, including HTTP, HTTPS, FTP, and more. When working with web services, cURL is often used for making requests, such as GET, POST, PUT, and DELETE.

Preparing JSON Data

Before posting JSON data, we need to prepare it. In PHP, you can create an array of data that you want to send. Then, use the json_encode() function to convert this array into a JSON string.

$data = array(
    "first_name" => "First name",
    "last_name" => "Last name",
    "email" => "[email protected]"
);

$jsonData = json_encode($data);

Configuring cURL for POST Requests

To post data using cURL, you need to initialize a cURL session with curl_init(), set the URL where the data will be posted, and then configure the options for your request.

$url = 'http://example.com/api/endpoint';

$ch = curl_init($url);

// Set the request method to POST
curl_setopt($ch, CURLOPT_POST, 1);

// Set the JSON data as the POST fields
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonData);

// Set the Content-Type header to application/json
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type:application/json'));

// Return the transfer as a string instead of outputting it directly
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

Executing the Request and Handling the Response

After setting up your cURL session, you can execute the request with curl_exec() and then close the session with curl_close(). The response from the server will be stored in the variable specified by CURLOPT_RETURNTRANSFER.

$response = curl_exec($ch);

if ($response === false) {
    echo 'cURL Error: ' . curl_error($ch);
} else {
    echo $response;
}

curl_close($ch);

Receiving JSON Data on the Server Side

When receiving JSON data on a server, you can access it using file_get_contents("php://input"), which reads the raw input of the request body. Then, use json_decode() to convert the JSON string back into a PHP array or object.

$jsonStr = file_get_contents("php://input");
$data = json_decode($jsonStr, true); // Use true as the second argument for associative arrays

print_r($data);

Conclusion

Posting JSON data with PHP cURL involves preparing your data as a JSON string, configuring cURL to send this data in a POST request, and then handling the server’s response. By following these steps, you can effectively interact with APIs or send data between servers using JSON payloads.