Remove unknown text appearing on page - php

Question

I have used a widget called addthisevent to allow users to add a class booking to their calendar. It is all working as indented but when I echo the link to the page I get a random ‘1’ next to the button. As you can see here -- http://oi60.tinypic.com/10fu8ac.jpg --
==add_event.php==
<?php
//Call session variables
$start_time = $_SESSION['class_time_start'];
$end_time = $_SESSION['class_time_end'];
$date = $_SESSION['class_date'];
$class_name = $_SESSION['class_name'];
$client_F_name = $_SESSION['firstname'];
$client_L_name = $_SESSION['lastname'];
$client_email = $_SESSION['email'];
//echo addthisevent script
echo '<script type="text/javascript" src="https://addthisevent.com/libs/ate-latest.min.js"></script>';
//echo addthisevent with the variables in place, ready to be converted using the JS function
echo '<a href="http://example.com/link-to-your-event" title="Add to Calendar" class=" addthisevent" id="addthisevent">'
, 'Add to Calendar'
, '<span class="_start">' . $date . ' ' . $start_time . '</span>'
, '<span class="_end">' . $date . ' ' . $end_time . '</span>'
, '<span class="_zonecode">36</span>'
, '<span class="_summary">' . $class_name . ' Class</span>'
, '<span class="_description">Your ' . $class_name . ' class with ****</span>'
, '<span class="_location">*****</span>'
, '<span class="_organizer">*****</span>'
, '<span class="_organizer_email">******</span>'
, '<span class="_facebook_event">*****</span>'
, '<span class="_all_day_event">false</span>'
, '<span class="_date_format">YYYY/MM/DD</span>'
, '</a>';
?>
Let me know if you need more code as I understand this is a weird issue I'm having.
I really can't work out what is causing it. I know it is definitely coming from the php above. If there is a way to fix this issue or just to simply remove the '1' after the page has loaded as a workaround that would be great
Thanks
The page link is http://217.37.5.115/content/temppage.php
you will need to select the dropdown boxes for it to appear
In short:
I use this function below to run a php script when the value of one of the dropdown boxes changes
===temppage.php (main page)===
<script>
function class_space_Update(str) {
if (str == "") {
document.getElementById("class_spaces").innerHTML = "";
return;
} else {
if (window.XMLHttpRequest) {
//code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp = new XMLHttpRequest();
} else {
//code for IE6, IE5
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
document.getElementById("class_spaces").innerHTML = xmlhttp.responseText;
addthisevent.refresh();
}
}
xmlhttp.open("GET", "../includes/get/class_spaces.php?id=" + str, true);
xmlhttp.send();
}
}
</script>
===class_spaces.php===
<?php
//Set session variables
//Session 'class_time_start'
$_SESSION['class_time_start'] = $start_time;
//Session 'class_time_end'
$_SESSION['class_time_end'] = $end_time;
//Session 'class_date'
$_SESSION['class_date'] = $date;
//Session 'space_left'
$_SESSION['space_left'] = $space_left;
//Include add_event.php
echo include_once ($_SERVER["DOCUMENT_ROOT"] . "/includes/add_event.php");
//Close MySQLi connection
mysqli_close($mysqli);
?>
This isn't all of that file as it isn't really necessary.
If I comment out the echo include_once add_event.php part then the '1' does not appear.

Answer 1

Quick solution I can offer for you is:
<?php
//Call session variables
$start_time = (isset($_SESSION['class_time_start']))?$_SESSION['class_time_start']:'';
$end_time = (isset($_SESSION['class_time_end']))?$_SESSION['class_time_end']:'';
$date = (isset($_SESSION['class_date']))?$_SESSION['class_date']:'';
$class_name = (isset($_SESSION['class_name']))?$_SESSION['class_name']:'';
$client_F_name = (isset($_SESSION['firstname']))?$_SESSION['firstname']:'';
$client_L_name = (isset($_SESSION['lastname']))?$_SESSION['lastname']:'';
$client_email = (isset($_SESSION['email']))?$_SESSION['email']:'';
//echo addthisevent script
ob_start();
echo '<script type="text/javascript" src="https://addthisevent.com/libs/ate-latest.min.js"></script>';
//echo addthisevent with the variables in place, ready to be converted using the JS function
echo '<a href="http://example.com/link-to-your-event" title="Add to Calendar" class=" addthisevent" id="addthisevent">'
, 'Add to Calendar'
, '<span class="_start">' . $date . ' ' . $start_time . '</span>'
, '<span class="_end">' . $date . ' ' . $end_time . '</span>'
, '<span class="_zonecode">36</span>'
, '<span class="_summary">' . $class_name . ' Class</span>'
, '<span class="_description">Your ' . $class_name . ' class with ****</span>'
, '<span class="_location">*****</span>'
, '<span class="_organizer">*****</span>'
, '<span class="_organizer_email">******</span>'
, '<span class="_facebook_event">*****</span>'
, '<span class="_all_day_event">false</span>'
, '<span class="_date_format">YYYY/MM/DD</span>'
, '</a>';
exit();