How to make checkbox info append to email

I have 3 checkboxes on my contact form. The form works with exception to the checkboxes.. The boxes are selectable but once hitting the "submit" button the selection shows up on the "Thank you for you comment" page. I cannot figure out how to get the checkbox selection to appear in the actual email.

I have tried all sorts of php functions that I have found people to be using in forums and tutorials. Nothing appends the checkbox info to the email. I can't seem to find anyone who knows how to do this.

The 'implode' function does not work. The 'echo' function does not work. The 'array' function does not work. What could be going on?

Here is my html:

<section class="contact">   
    <form id="contact" action="html_form_send.php" method="post">
    <fieldset title="About you">
    <legend><span>About you</span></legend>
      <label for="name">Name</label>
      <input type="text" name="name" id="name" tabindex="10"  class="txtinput" placeholder="Your name" required>
      <label for="email">Email</label>
      <input type="email" name="email" id="email" tabindex="20" class="txtinput" placeholder="valid email" required>
      </fieldset>
      <fieldset title="Your turn">
      <legend><span>Your turn</span></legend>
    <p>What, exactly then, are you after?</p>
    <div>
        <div class="tag">Checkbox1</div>         
        <input type="checkbox" id="checkbox-1-1" name="option[ ]" class="regular-checkbox big-checkbox" value="salvation" /></input><label for="checkbox-1-1"></label>
   </div>
   <div>
        <div class="tag">Checkbox2</div>
        <input type="checkbox" id="checkbox-2-1" name="option[ ]" class="regular-checkbox big-checkbox" value="question" /><label for="checkbox-2-1"></label>
  </div>
  <div>
        <div class="tag">Checkbox3</div>
        <input type="checkbox" id="checkbox-3-1" name="option[ ]" class="regular-checkbox big-checkbox" value="other" /><label for="checkbox-3-1"></label>
  </div>
       <label for="comment" class="inline"></label>
          <label for="discourse">Write your comments here</label>
         <textarea id="discourse" name="discourse" tabindex="30" class="txtinput" rows="7" placeholder="This is where your thoughts go">
         </textarea>

    <section id="buttons">
    <input type="reset" name="reset" id="resetbtn" class="resetbtn" value="Reset">
    <input type="submit" name="submit" id="submitbtn" class="submitbtn" tabindex="40" value="Send away!">
    <br style="clear:both;">
    </section>

Here is my php:

<?php
if(isset($_POST['email'])) {

    // CHANGE THE TWO LINES BELOW
    $email_to = "email@email.org";

    $email_subject = "website feedback";


    function died($error) {
        // your error code can go here
        echo "We're sorry, but there's errors found with the form you submitted.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }

    // validation expected data exists
    if(!isset($_POST['name']) ||
        !isset($_POST['email']) ||
        !isset($_POST['discourse'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }

    $name = $_POST['name']; // required
    $email_from = $_POST['email']; // required
    $discourse = $_POST['discourse']; // not required   $comments = $_POST['comments']; // required

    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
  if(!preg_match($email_exp,$email_from)) {
    $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
  }
    $string_exp = "/^[A-Za-z .'-]+$/";
  if(!preg_match($string_exp,$name)) {
    $error_message .= 'The Name you entered does not appear to be valid.<br />';
  }
   if(strlen($discourse) < 2) {
    $error_message .= 'The Comments you entered do not appear to be valid.<br />';
  }
  if(strlen($error_message) > 0) {
    died($error_message);
  }
    $email_message = "Form details below.\n\n";

    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }

    $email_message .= "Name: ".clean_string($name)."\n";
    $email_message .= "Email: ".clean_string($email_from)."\n";
    $email_message .= "Comments: ".clean_string($discourse)."\n";

    if(isset($_POST["submit"])) //Checks if the send button is pressed
    {
        echo $_POST["name"]; //print your name
        echo $_POST["email"]; //print your email

        //check all the checkboxes if anyone is checked. this is a lot of work to do.
        //All checkboxes are checked one by one
    if(isset($_POST["salvation"]))
        echo $_POST["salvation"];

    if(isset($_POST["question"]))
        echo $_POST["question"];

    if(isset($_POST["other"]))
        echo $_POST["other"];    }
        if(isset($_POST["submit"])) //Checks if the send button is pressed
   {
    echo $_POST["name"]; //print your name
    echo $_POST["email"]; //print your email

    if(isset($_POST["option"])) //checks if any interest is checked
    {
        foreach($_POST["option"] as $value) //Iterate the interest array and get the values
        {
            echo  $value;  //print the values          }         }     }


  // create email headers
  $headers = 'From: '.$email_from."\r\n".
  'Reply-To: '.$email_from."\r\n" .
  'X-Mailer: PHP/' . phpversion();
  @mail($email_to, $email_subject, $email_message, $headers);  }
  ?>

  <!-- place your own success html below -->
        <script language="javascript" type="text/javascript">
        alert('Thank you for contacting us.');
        window.location = 'feedbackform.html';
        </script>    
  <?php
  die();
  ?>