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

    // Sends Email
    $email_to = "name@email.com";

    $email_subject = "Subject";

<form name="htmlform" method="post" action="html_form_send.php">
<table width="450px">
</tr>
<tr>
 <td valign="top">
  <label for="first_name">First Name *</label>
 </td>
 <td valign="top">
  <input  type="text" name="first_name" maxlength="50" size="30">
 </td>
</tr>

<tr>
 <td valign="top"">
  <label for="last_name">Last Name *</label>
 </td>
 <td valign="top">
  <input  type="text" name="last_name" maxlength="50" size="30">
 </td>
</tr>
<tr>
 <td valign="top">
  <label for="email">Email Address *</label>
 </td>
 <td valign="top">
  <input  type="text" name="email" maxlength="80" size="30">
 </td>

</tr>
<tr>
 <td valign="top">
  <label for="telephone">Telephone Number</label>
 </td>
 <td valign="top">
  <input  type="text" name="telephone" maxlength="30" size="30">
 </td>
</tr>
<tr>
 <td valign="top">
  <label for="comments">Comments *</label>
 </td>
 <td valign="top">
  <textarea  name="comments" maxlength="1000" cols="25" rows="6"></textarea>
 </td>

</tr>
<tr>
 <td colspan="2" style="text-align:center">
  <input type="submit" value="Submit">   ( <a href="http://www.freecontactform.com/html_form.php">HTML Form</a> )
 </td>
</tr>
</table>
</form>

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


    $email_to = "name@email.com";

    $email_subject = "Subject";


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

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

    $first_name = $_POST['first_name']; // required
    $last_name = $_POST['last_name']; // required
    $email_from = $_POST['email']; // required
    $telephone = $_POST['telephone']; // 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($string_exp,$first_name)) {
    $error_message .= 'The First Name you entered does not appear to be valid.<br />';
  }
  if(!preg_match($string_exp,$last_name)) {
    $error_message .= 'The Last Name you entered does not appear to be valid.<br />';
  }
  if(strlen($comments) < 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.nn";

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

    $email_message .= "First Name: ".clean_string($first_name)."n";
    $email_message .= "Last Name: ".clean_string($last_name)."n";
    $email_message .= "Email: ".clean_string($email_from)."n";
    $email_message .= "Telephone: ".clean_string($telephone)."n";
    $email_message .= "Comments: ".clean_string($comments)."n";


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

Thank you for your response.

<?php
}
die();
?>

$email_to = "name@email.com,abc@xyz.com,bdc@mnq.com, nnn@nnn.nnn";

<form action="script.php">
    <select name="to_email_index">
        <option value="0" selected>Support</option>
        <option value="1" selected>Feedback</option>
    </select>
    <input type="submit" value="Send"/>
</form>

if (!isset($_GET['to_email_index']))
    exit("Error");

$to_email = "support@me.com";
if ($_GET['to_email_index']=="1")
    $to_email = "feedback@me.com";