How do I POST JSON data using PHP Curl library?

To make an HTTP POST request with JSON data using the PHP Curl library, you need to first initialize the PHP Curl library by calling the curl_init() function. You can pass the target URL during initialization or set it later by calling the curl_setopt() function with the "CURLOPT_URL" parameter. To pass additional HTTP headers to the PHP POST request, you can call curl_setopt() with the CURLOPT_HTTPHEADER parameter. In this PHP Curl POST JSON Example, we send the "Accept: application/json" and "Content-Type: application/json" request headers to the server. The "Content-Type: application/json" request header specifies the type of data in the body of the POST message, and the "Accept: application/json" header tells the server that the client is expecting JSON in response to our POST request. The curl_exec() function performs the POST request. Click Execute to run the POST JSON with PHP Curl Library Example online and see the result.
How do I POST JSON data using PHP Curl library? Execute 
<?php
$url = "https://reqbin.com/echo/post/json";

$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_HTTPHEADER, array('Accept: application/json', 'Content-Type: application/json'));
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

$data = <<<DATA
{
  "Id": 78912,
  "Customer": "Jason Sweet",
  "Quantity": 1,
  "Price": 18.00
}
DATA;

curl_setopt($curl, CURLOPT_POSTFIELDS, $data);

$resp = curl_exec($curl);
curl_close($curl);

echo $resp;
?>
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What is JSON?

JSON (JavaScript Object Notation) is a text-based, language-independent format for storing and transferring data over a network. JSON reaches from JavaScript and has a syntax analogous to JavaScript but can be used separately from it. JSON is used for client-server communication in mobile and web applications written in many programming languages, including PHP, JavaScript, Python, Java, C++, C#, Go, and many others.

What is PHP Curl Library?

Curl allows you to interact with servers through various types of protocols, including HTTP, HTTPS, FTP, and others. The Libcurl library supports HTTPS certificates, HTTP GET, POST, PUT, PATCH, and other HTTP methods, FTP file upload (FTP file upload can also be done with PHP FTP extension), proxy, cookies, user authentication, and HTML forms based upload. PHP Curl library is an extension of PHP that allows making HTTP requests. To use PHP Curl features, you need to install libcurl 7.10.5 or later and compile PHP with Curl support. The behavior of the PHP Curl functions is affected by the curl.cainfo setting in the php.ini file.

How to make POST requests using the PHP Curl Library?

To use the Curl library to send POST requests, you can follow these steps:

  • Initialize a Curl session with function curl_init()
  • Pass additional parameters wih the curl_setopt() function:
    • Target URL with the "CURLOPT_URL" option.
    • Additional HTTP headers with the "CURLOPT_HEADER" parameter.
    • Data with "CURLOPT_POSTFIELDS" parameter.
    • Set the "CURLOPT_RETURNTRANSFER" to "true" if need to return the string instead of printing it out
  • Start a Сurl session with the curl_exec() function
  • Close the Сurl session we created with the curl_close() function
  • Output the return string
PHP POST Curl Example
<?php
$url = "https://reqbin.com/echo/post/json";

$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_HTTPHEADER, array("Accept: application/json"));
curl_setopt($curl, CURLOPT_POSTFIELDS, "POST DATA");
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

$resp = curl_exec($curl);
curl_close($curl);

echo $resp;
?>

See also

PHP Curl POST JSON Related API examples and articles