CMS records conflict with php contact form

The php contact form I use conflicts with the CMS records after the contact delivery session has run, thanking the user for the inquiry. 

Here's the error I receive: 

Notice: Undefined variable: body in /data/17/1/113/93/1602093/user/1726350/htdocs/contact-hudson-valley-wedding-florist.php on line 96 Notice: Undefined variable: _SESSION in /data/17/1/113/93/1602093/user/1726350/htdocs/contact-hudson-valley-wedding-florist.php on line 105 Notice: Undefined index: security_code in /data/17/1/113/93/1602093/user/1726350/htdocs/contact-hudson-valley-wedding-florist.php on line 105

Here's the php code I use for the contact form. Any suggestions on resolving this? 

<?php if(isset($_POST['send'])){
$emailFrom = "Website Inquiry";
$emailTo = "email address goes here";
$subject = "General Inquiry";

$name = strip_tags($_POST['name']);  
$phone = strip_tags($_POST['phone']); 
$email = strip_tags($_POST['email']); 
$message = strip_tags(stripslashes($_POST['message'])); 


$body .= "Name: ".$name."\n";
$body .= "Phone: ".$phone."\n";
$body .= "Email: ".$email."\n";
$body .= "Message: ".$message."\n";


$headers = "From: ".$emailFrom."\n";
$headers .= "Reply-To:".$email."\n";

if($_SESSION['security_code'] == $_POST['security_code']){
$success = mail($emailTo, $subject, $body, $headers);
if ($success){
echo '<p class="contact-message-done">Thank you for your inquiry. We will contact you shortly.</p>';
} 
} else {
echo '<p class="contact-message-done">Your submission was invalid. Please make sure you filled in all the appropriate fields and please submit again.</p>';
}
} else {
?>