How does the PHP cURL library send a POST request containing JSON data?

This article will guide you how to use PHP's cURL library to send POST requests containing JSON data. This is very common when interacting with external APIs.

Question: How to send a POST request using cURL and include JSON data as the request body?

Solution:

First, initialize the cURL session:

 $curl = curl_init();

Then, use curl_setopt_array() to set the cURL options. Key options include:

• CURLOPT_URL : The destination URL address (for example: 'http://localhost/api/endpoint' ).
• CURLOPT_RETURNTRANSFER : Set to true to return the server response as a string instead of outputting it directly.
• CURLOPT_ENCODING : Set encoding (usually empty string '' ).
• CURLOPT_MAXREDIRS : Maximum number of redirects (for example: 10 ).
• CURLOPT_TIMEOUT : Timeout time (for example: 0 means infinite waiting).
• CURLOPT_FOLLOWLOCATION : Set to true to allow follow-up redirects.
• CURLOPT_HTTP_VERSION : HTTP version (for example: CURL_HTTP_VERSION_1_1 ).
• CURLOPT_CUSTOMREQUEST : Set to 'POST' , specifying the POST request.
• CURLOPT_POSTFIELDS : The body content of the POST request, here is a JSON string. Make sure the JSON string is formatted correctly . You can use PHP's json_encode() function to ensure the format is correct.
• CURLOPT_HTTPHEADER : Sets the HTTP request header, including 'Content-Type: application/json' , to inform the server that the request body is JSON format, and other necessary header information, such as cookies.

Complete code example:

 <?php $curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => 'http://localhost/api/endpoint',
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => '',
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => true,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => 'POST',
  CURLOPT_POSTFIELDS => json_encode([
    "appid" => "111",
    "secret" => "ddd111",
    "an" => "xxx"
  ]),
  CURLOPT_HTTPHEADER => [
    'Content-Type: application/json',
    'Cookie: lang=zh-cn; ssid=02bebb340032d3a9e4b15463dd7d0eaa'
  ],
]);

$response = curl_exec($curl);

curl_close($curl);
echo $response;
?>

Finally, use curl_exec() to execute the request and curl_close() closes the session. echo $response; outputs the server's response.

Tip: You can use tools such as Postman to generate code examples for different languages ​​and libraries as a reference. Be sure to double-check your JSON data format and settings for all cURL options to ensure the correctness of the request. Refer to PHP's cURL documentation for more detailed information.

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