CURLOPT_READFUNCTION

CURLOPT_READFUNCTION is one of the accepted parameters for curl_setopt parameter #2.

CURLOPT_READFUNCTION — A callback accepting three parameters. The first is the cURL resource, the second is a stream resource provided to cURL through the option CURLOPT_INFILE, and the third is the maximum amount of data to be read. The callback must return a string with a length equal or smaller than the amount of data requested, typically by reading it from the passed stream resource. It should return an empty string to signal EOF.

CURLOPT_READFUNCTION = 20012;