Regarding PHP CURL
Pass a pointer to a double to receive the time, in seconds, it took from the start until the file transfer is just about to begin. This includes all pre-transfer commands and negotiations that are specific to the particular protocol(s) involved
Pass a pointer to a double to receive the time, in seconds, it took from the start until the first byte is just about to be transferred. This includes CURLINFO_PRETRANSFER_TIME and also the time the server needs to calculate the result