if(isset($_POST['submit'])) {
     
    // EDIT THE 2 LINES BELOW AS REQUIRED
    $email_to = "[email protected]";
    $email_subject = "письмо от Техниона";
     
     
    function died($error) {
        // your error code can go here
        echo $error."<br /><br />";
        die();
    }
     
    // validation expected data exists
    if(!isset($_POST['name']) ||
        !isset($_POST['last_name']) ||
        !isset($_POST['email']) ||
        !isset($_POST['phone']) ||
        !isset($_POST['city'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');      
    }
     
    $first_name = trim(strip_tags($_POST['name'])); // required
    $last_name = trim(strip_tags($_POST['last_name'])); // required
    $email_from = trim(strip_tags($_POST['email'])); // required
    $telephone = trim(strip_tags($_POST['phone'])); // not required
    $city = trim(strip_tags($_POST['city'])); // 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)) {
    $error_message .= "<li class='error'>".$email_error."</li><br/>";
  }
    $string_exp = "/^[A-Za-z .-]+$/";
  if(!preg_match($string_exp,$first_name)) {
    $error_message .= "<li class='error'>".$name_error."</li><br/>";
  }
  if(!preg_match($string_exp,$last_name)) {
    $error_message .= "<li class='error'>".$last_name_error."</li><br/>";
  }
  if(strlen($city) < 2) {
    $error_message .= "<li class='error'>".$city_error."</li><br/>";
  }
 
 
    if( !preg_match("/^[0-9]{10}$/", $telephone) || strlen($telephone) < 10) {
    $error_message .= "<li class='error'>".$phone_error."</li><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);
    }
     
    $email_message .= "First Name: ".clean_string($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";
    $email_message .= "city: ".clean_string($city)."\n";
 
     
     
// 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, $headers);
echo"<li class='error2'>".$successfully_msg."</li><br/>";
die();
 }

<?php

if(isset($_POST['submit']))
{
     
    // EDIT THE 2 LINES BELOW AS REQUIRED
    $email_to = "[email protected]";
    $email_subject = "письмо от Техниона";
     
     
    function died($error)
    {
        // your error code can go here
        echo $error."<br /><br />";
        die();
    }
   
   
    if(isset($_POST['hidden_field_name']) && '' !== trim($_POST['hidden_field_name']))
    {
    died('This field was supposed to be empty');
  }
     
     
    // validation expected data exists
    if(!isset($_POST['name'],$_POST['last_name'],$_POST['email'],$_POST['phone'],$_POST['city']))
    {
        died('We are sorry, but there appears to be a problem with the form you submitted.');      
    }
     
    $first_name = trim(strip_tags($_POST['name'])); // required
    $last_name = trim(strip_tags($_POST['last_name'])); // required
    $email_from = trim(strip_tags($_POST['email'])); // required
    $telephone = trim(strip_tags($_POST['phone'])); // not required
    $city = trim(strip_tags($_POST['city'])); // 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))
  {
    $error_message .= "<li class='error'>".$email_error."</li><br/>";
  }
 
  $string_exp = "/^[A-Za-z .-]+$/";
  if(!preg_match($string_exp,$first_name))
  {
    $error_message .= "<li class='error'>".$name_error."</li><br/>";
  }
 
 
  if(!preg_match($string_exp,$last_name))
  {
    $error_message .= "<li class='error'>".$last_name_error."</li><br/>";
  }
 
  if(strlen($city) < 2)
  {
    $error_message .= "<li class='error'>".$city_error."</li><br/>";
  }
 
 
    if( !preg_match("/^[0-9]{10}$/", $telephone) || strlen($telephone) < 10)
    {
    $error_message .= "<li class='error'>".$phone_error."</li><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);
  }

  $email_message .= "First Name: ".clean_string($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";
  $email_message .= "city: ".clean_string($city)."\n";
 
     
     
  // create email headers
  $headers = 'From: '.$email_from."\r\n".
  'Reply-To: '.$email_from."\r\n" .
  'X-Mailer: PHP/' . phpversion();
 
  // NEVER NEVER NEVER NEVER NEVER NEVER
  // NEVER EVER
  // NEVER EVER USE
  // DO YOU HEAR ME? NEEEEEEEEVER
  // USE THE @ sign
  // NEVER!!!
  // BUT..
  // NO, NO BUT. NO EVER.
  $sent = mail($email_to, $email_subject, $email_message, $headers);
 
  if(!$sent)
  {
      echo "Sorry, couldn't send your email";
  }
  else
  {
    echo"<li class='error2'>".$successfully_msg."</li><br/>";
  }
  die();
 }

if('' === trim($_POST['fieldname'])