PHP Manual: Incrementally parse data into buffer

bool mailparse_msg_parse(resource $mimemail, string $data)

Incrementally parse data into the supplied mime mail resource.

This function allow you to stream portions of a file at a time, rather than read and parse the whole thing.

mimemail: A valid MIME resource.
data: Note:
The final chunk of data is supposed to end with a newline (CRLF); otherwise the last line of the message will not be parsed.

Returns true on success or false on failure.