How to send data as JSON in a Guzzle POST request in PHP?

To send data as JSON in a Guzzle POST request in PHP, you can use the json option provided by Guzzle. Here's an example:

use GuzzleHttp\Client;

$client = new Client();

$body = [
    'key1' => 'value1',
    'key2' => 'value2'
];

$response = $client->post('https://example.com/api/endpoint', [
    'json' => $body
]);

echo $response->getBody();

In this example, we create a new instance of the Guzzle Client class. We define an array $body containing the data we want to send. We then make a POST request to the specified URL, and pass the $body array as the value of the json option. Guzzle will automatically serialize the array into JSON and send it in the request.

Note that you need to have Guzzle installed in your project for this code to work. You can install Guzzle using Composer by running composer require guzzlehttp/guzzle in your project directory.