How to Post JSON Data using cURL in PHP

JSON is the most popular data format on the web because it is natively supported in JavaScript and human-readable.

As such, many APIs support the ability to send and receive JSON data.

In this tutorial, we will learn how to send JSON data to a URL using cURL in PHP.

Sending JSON Data to a URL

To send JSON data to a URL, first let's define the array we want to send:

PHP
$data = [
    'name' => 'John Doe',
    'age' => 30
];

Now let's encode the array as JSON:

PHP
$json = json_encode($data);

Not that we have our JSON, let's initialize a cURL request:

PHP
$ch = curl_init();

Now let's apply a few options:

PHP
curl_setopt($ch, CURLOPT_URL, 'https://example.com/api');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Content-Type: application/json',
    'Content-Length: ' . strlen($json)
]);

Finally, let's execute the request:

PHP
$output = curl_exec($ch);

Now, we can close the cURL request:

PHP
curl_close($ch);

Taken all together, we can write a reusable function for this:

PHP
$data = [
    'name' => 'John Doe',
    'age' => 30
];

function post_json($url, $data) {
    $json = json_encode($data);
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json',
        'Content-Length: ' . strlen($json)
    ]);
    $output = curl_exec($ch);
    curl_close($ch);
    return $output;
}

$output = post_json('https://example.com/api', $data);

echo $output;

Conclusion

In this post, we learned how to send JSON data to a URL using cURL in PHP.

Simply initialize a new cURL request, apply a few options, and execute the request with the given url and data.

Thanks for reading!

Then, we can close the cURL request and return the output.

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