A simple Mailer class

Mailer.php

<?php
/**
 * Mailer.php
 *
 * @author  Michael Pratt <pratt@hablarmierda.net>
 * @link    http://www.michael-pratt.com/
 * @license MIT
 */

namespace Mailer;

/**
 * A very simple mailer class that uses php's default mail function.
 *
 * Usage:
 * $mailer = new Mailer('from@host.tld', 'to@host.tld', 'subject', 'body');
 * try {
 *     $mailer->send();
 * } catch(\Exception $e) {}
 */
class Mailer
{
    /** @var string The email where the email is going to be sent **/
    protected $to;

    /** @var string The email from where is going to be sent **/
    protected $from;

    /** @var string The subject of the email **/
    protected $subject;

    /** @var string The body of the email **/
    protected $body;

    /** @var array Headers of the email **/
    protected $headers = array();

    /**
     * Construct
     *
     * @param string $from
     * @param string $to
     * @param string $subject
     * @param string $body
     * @param bool $html Send the content as html or as plain text.
     * @return void
     */
    public function __construct($from, $to, $subject, $body, $html = true)
    {
        $this->from = $from;
        $this->addMailHeader('From', $this->from);
        $this->addMailHeader('Reply-To', $this->from);
        $this->addMailHeader('Return-Path', $this->from);
        $this->addMailHeader('X-mailer', 'PHP/SimpleMailer');
        $this->addMailHeader('MIME-Version', '1.0');
        // $this->addMailHeader('Content-Transfer-Encoding', '8bit');

        if ($html) {
            $this->addMailHeader('Content-type', 'text/html; charset=UTF-8');
        } else {
            $this->addMailHeader('Content-type', 'text/plain; charset=UTF-8');
        }

        $this->to = $to;
        $this->subject = $subject;
        $this->body = $body;
    }

    /**
     * Appends stuff to the mail header
     *
     * @param string $header The name of the header
     * @param string $value  The content of the header
     * @return void
     */
    public function addMailHeader($header, $value)
    {
        $this->headers[$header] = $value;
    }

    /**
     * Sends the mail.
     *
     * @return bool
     *
     * @throws InvalidArgumentException when an invalid Email Address is given
     * @throws RuntimeException if the operation was not successful.
     *
     * @codeCoverageIgnore
     */
    public function send()
    {
        if (!filter_var($this->from, FILTER_VALIDATE_EMAIL)) {
            throw new \InvalidArgumentException('The address ' . $this->from . ' does not appear to be valid!');
        } elseif (!filter_var($this->to, FILTER_VALIDATE_EMAIL)) {
            throw new \InvalidArgumentException('The address ' . $this->to . ' does not appear to be valid!');
        }

        $headers = '';
        foreach ($this->headers as $key => $value) {
            $headers .= $key . ": " . $value . "\r\n";
        }

        if (!mail($this->to, '=?utf-8?B?' . base64_encode($this->subject) . '?=', $this->body, $headers)) {
            throw new \RuntimeException('Error sending mail');
        }

        return true;
    }
}

?>