Get particular section structure of message

I make a function to fetch the structure of a particulat section of a message, and I test it with some special mails and it works well. But for I am not so familiar with mime-types, I need more suggest and help. function getCurrentStruct($pi_msgid, $ps_part=1) { //$o_struct = $this->getStructure($pi_msgid); $o_struct = imap_fetchstructure($mbox, $pi_msgid); //$ps_part is a string like "4.3.3" if (!array_key_exists("parts", get_object_vars($o_struct))) { //$this->pushError("No such part"); //call imap_errors() and return the last error return new PEAR_Error($this->getError()); } foreach (explode(".", $ps_part) as $i) { if (!array_key_exists("parts", get_object_vars($o_struct)) || !is_array($o_struct->parts)) { return new PEAR_Error("No such part"); } $a_tmp = $o_struct->parts; if ($a_tmp[0]->type == 1) { // && (strtoupper($a_tmp[0]->subtype)=="MIXED") { $a_tmp = $a_tmp[0]->parts; } $o_struct = $a_tmp[$i-1]; } return $o_struct; }