How Does CURLOPT_POSTFIELDS Handle String and Array Data in cURL POST Requests?

CURLOPT_POSTFIELDS and POST Data Format in cURL

When utilizing cURL for POST requests, the format of data to be posted through CURLOPT_POSTFIELDS depends on the nature of the data.

String Data:

If sending a string, such as "first=John&last=Smith", you must encode it using urlencode(). This prevents characters like ampersands (&) from interfering with the data transmission.

Array Data:

For array data, cURL automatically sets the Content-Type header to multipart/form-data, which is essential for sending multipart form data. Each key-value pair in the array corresponds to a form field and its value.

For instance, if you have an array $data = ['first' => 'John', 'last' => 'Smith'], you can set CURLOPT_POSTFIELDS as follows:

curl_setopt($ch, CURLOPT_POSTFIELDS, $data);

cURL will automatically generate the necessary multipart form data encoding.

Helper Function:

You can simplify the process of building the query string for array data using the http_build_query() function:

$query = http_build_query($data, '', '&');
curl_setopt($ch, CURLOPT_POSTFIELDS, $query);

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