PHP尝试添加将附件发送到工作“联系我们”表单的功能

我有一个朋友要求我修改她网站的联系表格以请求电话号码以及添加照片附件的能力。我已经添加了请求和发送电子邮件的电话号码所需的代码，但添加附加照片文件的功能超出了我目前的知识范围。有人可以看看代码并告诉我如何添加将文件附加到消息的功能吗？我要做的就是在当前消息字段下方添加它，但事实证明它比我预期的要复杂得多。由于我尝试的所有内容都破坏了当前表单，因此我删除了添加附件的代码尝试，并且我正在发布当前有效的代码。我希望对php有更好掌握的人可以帮助我们解决这个问题。

    <?php
      //set the level of error reporting
        error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);  
      // Set-up these 3 parameters
      $to = 'any@somewhere.net';
      $subject = 'Question from The website';
      $contact_submitted = 'Your message has been sent.';
      function email_is_valid($email) {
        return preg_match('/^[A-Z0-9._%+-]+@[A-Z0-9.-]+'.[A-Z]{2,4}$/i',$email);
      }
      if (!email_is_valid($to)) {
        echo '<p style="color: red;">You must set-up a valid (to) email address before this contact page will work.</p>';
      }
      if (isset($_POST['contact_submitted'])) {
        $return = "'n'r";
        $youremail = trim(htmlspecialchars($_POST['your_email']));
        $yourname = stripslashes(strip_tags($_POST['your_name']));
        $yourphone = trim(htmlspecialchars($_POST['your_phone']));
        $yourmessage = stripslashes(strip_tags($_POST['your_message']));
        $contact_name = "Name: ".$yourname;
        $contact_email = "Email Address: ".$youremail;
        $contact_phone = "Phone: ".$yourphone;
        $message_text = "Message: ".$yourmessage;
        $user_answer = trim(htmlspecialchars($_POST['user_answer']));
        $answer = trim(htmlspecialchars($_POST['answer']));
        $message = $contact_name . $return . $contact_email . $return . $contact_phone . $return . $return . $message_text;
        $headers = "From: ".$youremail;
        if (email_is_valid($youremail) && !eregi("'r",$youremail) && !eregi("'n",$youremail) && $yourname != "" && $yourphone != "" && $yourmessage != "" && substr(md5($user_answer),5,10) === $answer) {
          mail($to,$subject,$message,$headers);
          $yourname = '';
          $youremail = '';
          $yourphone = '';
          $yourmessage = '';
          echo '<p style="color: blue;">'.$contact_submitted.'</p>';
        }
        else echo '<p style="color: red;">Please enter your name, a valid email address, your message and the answer to the simple maths question before sending your message.</p>';
      }
      $number_1 = rand(1, 9);
      $number_2 = rand(1, 9);
      $answer = substr(md5($number_1+$number_2),5,10);
    ?>
    <form id="contact" action="contact.php" method="post">
      <div class="form_settings">
        <p><span>Name:</span><input class="contact" type="text" name="your_name" value="<?php $yourname; ?>" /></p>
        <p><span>Email Address:</span><input class="contact" type="text" name="your_email" value="<?php $youremail; ?>" /></p>
        <p><span>Phone Number:</span><input class="contact" type="text" name="your_phone" value="<?php $yourphone; ?>" /></p>
        <p><span>Message:</span><textarea class="contact textarea" rows="1" cols="50" name="your_message"><?php $yourmessage; ?></textarea></p>
        <p style="line-height: 1.7em;">To help prevent spam, please enter the answer to this question:</p>
        <p><span><?php echo $number_1; ?> + <?php echo $number_2; ?> = ?</span><input type="text" name="user_answer" /><input type="hidden" name="answerswer" value="<?php echo $answer; ?>" /></p>
        <p style="padding-top: 15px"><span>&nbsp;</span><input class="submit" type="submit" name="contact_submitted" value="send" /></p>
      </div>
    </form>

如果有人能弄清楚这一点，我将永远感激不尽。