my PHP-Process file

<?php
    $event_date = $_POST['event_date'];
    $name = $_POST['full_name'];
    $event_type = $_POST['event_type'];
    $telephone = $_POST['telephone'];
    $email = $_POST['email'];


   $email_from = 'mywebsiteemail@gmail.com';

    $email_subject = "New Form submission from your website";

    $email_body = "You have received a new message via your websites form from $name.\n".
                            "The date requested for the event is:\n     $event_date\n".

    "The type of event is:\n $event_type \n".

    "The customers contact telephone number is:\n $telephone \n".

    "From:\n $email \n".


  $to = "myclientsemail@gmail.com";
  $headers = "From: $email_from \r\n";
  $headers = "Reply-To: $email \r\n";
    mail($to,$email_subject,$email_body,$headers);




//Load thank you page once form is submitted

header ('Location: contact-thank-you.html');
exit();



?>

<?php

function IsInjected($str)
{
    $injections = array('(\n+)',
           '(\r+)',
           '(\t+)',
           '(%0A+)',
           '(%0D+)',
           '(%08+)',
           '(%09+)'
           );

    $inject = join('|', $injections);
    $inject = "/$inject/i";

    if(preg_match($inject,$str))
    {
      return true;
    }
    else
    {
      return false;
    }
}

if(IsInjected($visitor_email))
{
    echo "Bad email value!";
    exit;
}

error_reporting(-1);

?>