Mailer class for built-in PHP mail()

mailer.class.php

<?php

class Mailer
{

  protected $to = array();
  protected $cc = array();
  protected $bcc = array();
  protected $reply = array();
  protected $files = array();
  protected $headers = array();
  protected $content = array();

  protected $main_boundary = '';
  protected $extra_boundary = '';

  protected $subject= '';
  protected $from = '';



  private function __construct(){}


  public static function factory()
  {
    $out = new static;

    $out->main_boundary = md5(uniqid('--main-boundary'));
    $out->extra_boundary = md5(uniqid('--extra-boundary'));

    return $out;
  }


  public function add_to($test)
  {
    $this->to []= $test;
    return $this;
  }

  public function add_reply($test)
  {
    $this->reply []= $test;
    return $this;
  }

  public function add_bcc($test)
  {
    $this->bcc []= $test;
    return $this;
  }

  public function add_cc($test)
  {
    $this->cc []= $test;
    return $this;
  }

  public function add_file($file, $mime = '')
  {
    if (is_file($file)) {
      $mime = strpos($mime, '/') !== FALSE ? $mime : 'application/octet-stream';
      $this->files []= array($mime => $file);
    }
    return $this;
  }

  public function add_header($key, $val = '')
  {
    if (is_array($key)) {
      foreach ($key as $sub => $val) {
        $this->headers []= "$sub: $val";
      }
    } elseif ( ! is_numeric($key) && $val) {
      $this->headers []= "$key: $val";
    }

    return $this;
  }

  public function set_from($test, $name = '')
  {
    $this->from = $name ? "$name <{$test}>" : $test;
    return $this;
  }

  public function set_subject($text)
  {
    $this->subject = $text;
    return $this;
  }

  public function set_content($text)
  {
    $this->content = preg_split('/[\r\n]+/', $text);
    return $this;
  }

  public function add_content($text)
  {
    $this->content []= $text;
    return $this;
  }

  public function send()
  {
    $to   = join(', ', $this->to);
    $html = join("\n", $this->content);

    if (($content = $this->build_mail($html)) === FALSE) {
      return FALSE;
    }

    return @mail($to, $this->subject, $content, $this->get_headers());
  }

  public function reset()
  {
    $this->to = array();
    $this->cc = array();
    $this->bcc = array();
    $this->reply = array();
    $this->files = array();
    $this->headers = array();
    $this->content = array();

    $this->subject = '';
    $this->from = '';
  }



  private function get_attachments()
  {
    $out = '';

    foreach ($this->files as $one) {
      $mime = key($one);
      $file = $one[$mime];
      $name = basename($file);

      if ($tmp = chunk_split(base64_encode(read($file)))) {
        $out .= "--$this->main_boundary\nContent-Type: $mime; name=\"$name\"\n"
             .  "Content-Transfer-Encoding: base64\n"
             .  "Content-Disposition: attachment; filename=\"$name\"\n\n"
             .  "$tmp\n";
      }
    }

    return $out;
  }

  private function get_headers()
  {
    $out = "From: $this->from\nMIME-Version: 1.0\n"
         . 'Content-Type: ' . sprintf("multipart/%s; boundary=\"%s\"\n", $this->files ? 'mixed' : 'alternative', $this->main_boundary);

    $this->reply && $out .= sprintf("Reply-To: %s\n", join(', ', $this->reply));

    return $out;
  }

  private function build_mail($test)
  {
    // TODO: =HEX values?
    $plain = preg_replace('/\r?\n/', '<br />', str_replace("\t", '    ', $test));
    $plain = strip_tags(preg_replace('/<br\s*\/?' . '>/', "\n", $plain));

    $charset = 'UTF-8';
    $out     = "MIME-Version: 1.0\n"
             . "Content-Type: multipart/alternative; boundary=\"$this->main_boundary\"\n\n"
             . "This is a multi-part message in MIME format.\n\n"
             . "--$this->main_boundary\nContent-Type: text/plain; charset=\"$charset\"\n"
             . "Content-Transfer-Encoding: quoted-printable\n\n"
             . "$plain\n--$this->main_boundary\n"
             . "Content-Type: text/html; charset=\"$charset\"\n"
             . "Content-Transfer-Encoding: quoted-printable\n\n"
             . "$test\n\n--$this->main_boundary--";


    if ( ! empty($this->files)) {
      $files = $this->get_attachments();
      $out   = "This is a multi-part message in MIME format.\n\n"
             . "--$this->main_boundary\nContent-Type: multipart/alternative; boundary=\"$this->extra_boundary\"\n\n"
             . "--$this->extra_boundary\nContent-Type: text/plain; charset=\"$charset\"\n"
             . "Content-Transfer-Encoding: quoted-printable\n\n$plain\n"
             . "--$this->extra_boundary\nContent-Type: text/html; charset=\"$charset\"\n"
             . "Content-Transfer-Encoding: quoted-printable\n\n"
             . "$test\n\n--$this->extra_boundary--\n\n"
             . "$files\n--$this->main_boundary--";
    }

    return $out;
  }

}