I want to create a xml from a given string, i have a function but i didn't wrote it.It seems a bit cryptical too. Can please some one review it and give me some Ideas, how it could be written clearer for everybody?

/**
         * Converts arrays or SimpleXML-Objects into an XML-String
         * @params mixed Accepts an array or xml string with data to Post
         * @params integer DO NOT PROVIDE. Internal Usage for recursion only
         */
        private function mixedDataToXML($data, $level = 1) 
        {
                if(!$data){
                        return FALSE;
                }
                if(is_array($data)) {
                        $xml = '';
                        if ($level==1) {
                                $xml .= '<?xml version="1.0" encoding="ISO-8859-1"?>'."\n";
                        }
                        foreach ($data as $key => $value) {
                                $key = strtolower($key);
                                if (is_array($value)) {
                                        $multi_tags = false;
                                        foreach($value as $key2=>$value2) {
                                                if (is_array($value2)) {
                                                        $xml .= str_repeat("\t",$level)."<$key>\n";
                                                        $xml .= $this->mixedDataToXML($value2, $level+1);
                                                        $xml .= str_repeat("\t",$level)."</$key>\n";
                                                        $multi_tags = true;
                                                } else {
                                                        if (trim($value2)!='') {
                                                                if (htmlspecialchars($value2)!=$value2) {
                                                                        $xml .= str_repeat("\t",$level).
                                                                                        "<$key><![CDATA[$value2]]>".
                                                                                        "</$key>\n";
                                                                } else {
                                                                        $xml .= str_repeat("\t",$level).
                                                                                        "<$key>$value2</$key>\n";
                                                                }
                                                        }
                                                        $multi_tags = true;
                                                }
                                        }
                                        if (!$multi_tags and count($value)>0) {
                                                $xml .= str_repeat("\t",$level)."<$key>\n";
                                                $xml .= $this->mixedDataToXML($value, $level+1);
                                                $xml .= str_repeat("\t",$level)."</$key>\n";
                                        }
                                } else {
                                        if (trim($value)!='') {
                                                if (htmlspecialchars($value)!=$value) {
                                                        $xml .= str_repeat("\t",$level)."<$key>".
                                                                        "<![CDATA[$value]]></$key>\n";
                                                } else {
                                                        $xml .= str_repeat("\t",$level).
                                                                        "<$key>$value</$key>\n";
                                                }
                                        }
                                }
                        }
                        return $xml;
                }else{
                        return (string)$data;
                }
        }