PHP Mailer

<?php

class Mailer {
    protected $_boundary = false,
        $_charset = 'UTF-8',
        $_header = '',
        $_additional = '';
    public $is_html = false;

    public function setCharset($charset) {
        $this->_charset = $charset;
    }

    public function addHeader($name, $value) {
        $this->_headers[] = "$name: $value";
    }

    public function encode($data) {
        return '=?' . $this->_charset . '?B?' . base64_encode($data) . '?=';
    }

    public function setFrom($email, $name = null) {
        $this->addHeader('From', $name ? $this->encode($name) . " <$email>" : $email);
    }

    public function addAttachment($name, $data, $type = null) {
        if (!$this->_boundary) {
            $this->_boundary = uniqid();
        }
        if (!$type) {
            $type = 'application/octet-stream';
        }
        $this->_additional .= "--{$this->_boundary}\r\n";
        $this->_additional .= "Content-Type: $type; name=\"" . $this->encode($name) . "\"\r\n";
        $this->_additional .= "Content-Disposition: attachment\r\n";
        $this->_additional .= "Content-Transfer-Encoding: base64\r\n\r\n";
        $this->_additional .= chunk_split(base64_encode($data)) . "\r\n";
    }

    public function attachFile($filename, $content_type = null) {
        $this->addAttachment(basename($filename), file_get_contents($filename), $content_type);
    }

    public function send($addr, $subject = '', $message = '') {
        $message = chunk_split(base64_encode($message));
        $content_type = 'Content-Type: text/' . ($this->is_html ? 'html' : 'plain') . '; charset=' . $this->_charset;
        $content_transfer_encoding = 'Content-Transfer-Encoding: base64';
        $body = '';
        if ($this->_boundary) {
            $this->_headers[] = "Content-Type: multipart/mixed; boundary=\"{$this->_boundary}\"";
            $body .= "--{$this->_boundary}\r\n";
            $body .= "$content_type\r\n";
            $body .= "$content_transfer_encoding\r\n\r\n";
            $body .= "$message\r\n";
            $body .= $this->_additional;
            $body .= "--{$this->_boundary}--";
        }
        else {
            $this->_headers[] = $content_type;
            $this->_headers[] = $content_transfer_encoding;
            $body = $message;
        }
        return mail($addr, $this->encode($subject), $body, implode("\r\n", $this->_headers));
    }
}