how to fetch data from sql server database in php without refreshing the page

I assume that you have a page (application.php) that displays a table somewhere. And that you wish to fill that table with the data found in you database.

I'm not sure about WHEN you want these data to be refreshed. On button click or periodically (like ervery 5 seconds)... But it doesn't matter for what I explain below.

In application.php: Assemble all your page as you already know how.

But inside it, somewere, just insert an empty div where your table should show:

<div id="dynamicContent"></div>

Also add this script at the bottom of the page:

<script>
function getData(){
    PostData="";
    $.ajax({
        type: "POST",
        url: "function.php",
        data: PostData,
        cache: true,
        success: function(html){
            $(Destination).html(html);
        }
    });
}

getData();   // Trigger it on first page load !
</script>

There is 2 variables here... I named it "PostData" and "Destination".

About PostData:
You can pass data collected on the client side to your PHP function if needed. Suppose you'd need to pass your user's first and last name, You'd define PostData like this:

Fname=$("#Fname").val(); // user inputs
Lname=$("#Lname").val();
PostData="Fname="+Fname+"&Lname="+Lname;

In your function.php, you will retreive it like this (like any normal POST data):

$Fname=$_POST['Fname'];
$Lname=$_POST['Lname'];

If you do not need to pass data from your client side script to you server side PHP... Just define it empty.

PostData="";

Then, about Destination:
This is the place for the empty "dynamic div" id ( I named it "dynamicContent" above).
Don't forget about the hashtag (#) for an id or the dot for a class.
This is a jQuery selector.
So here, PostData would be defined like this:

Destination="#dynamicContent";

The result of the ajax request will land into that "dynamic div".
This WILL be the result of what's defined in function.php..

So, if you follow me, you have to build your table in function.php...
I mean the part where you do your database query and your while fetch.

echo "<table>";
echo "<tr><th>column title 1</th><th>column title 2</th></tr>"
while ($row = sqlsrv_fetch_array($stmt)){
    echo "<tr><td>" . $row['data1'] . "</td><td>" . $row['data2'] . "</td></tr>";
}
echo "</table>";

So if you have no data, the table will be empty.
You'll only get the table and table headers... But no row.
There is then no need for a function that checks if there is data or not.

Finally... About the trigger to refresh:
In application.php, you may place a button that fires getData()... Or you may define a setInterval.
It's up to you.

This is how I use ajax to refresh part of a page without reloading it completly.
Since ajax is new to you, I hope this answer will help.
;)

------------------------
EDIT based on Ariel's comment (2016-05-01)

Okay, I understand! Try this:

In application.php:

<div id="dynamicDiv"></div>


<script type="text/javascript">

    // timer to trigger the function every seconds
    var checkInterval = setInterval(function(){
        checkTicket();
    },1000);


    function checkTicket(){
        $.ajax({
            type: "POST",
            url: "function.php",
            data: "",
            cache: true,
            success: function(html){
                $("#dynamicDiv").html(html);
            }
        });      
    }

    function noMoreTikets(){
        clearInterval(checkInterval);
        window.location.replace("http://www.google.com");
    }
</script>

In function.php:

// Remove the "function is_ticket_able($conn){" function wrapper.
// Define $conn... Or include the file where it is defined.

// I assume that your query lookup works.

$query = "select number_of_tickets from [dbo].[TICKETS_LKUP] " ;
$stmt = sqlsrv_query($conn, $query);
while ($row = sqlsrv_fetch_array($stmt)) {
    $ticket = $row['number_of_tickets'];
}

// Add this instead of a return.
if($ticket>0){
    echo "There is still some tickets!";    // Text that will show in "dynamicDiv"
}else{
    ?>
    <script>
        $(document).ready(function(){
            noMoreTikets();
        });
    </script>
    <?php
}

Remember that your PHP scripts are executed server-side.
That is why your "return $ticket;" wasn't doing anything.

In this ajax way to call function.php, its script is executed alone, like a single page, without any relation with application.php, which was executed long ago.

It produces text (or javascript) to be served to the client.
If you want to pass a PHP variable to the client-side javascript, you have to echo it as javascript.

So here, if the PHP variable $ticket is more than zero, some text saying that there is still tickets available will show in "dynamicDiv" and the application page will not be refreshed. I suppose it shows a button or something that allows students to get a ticket.

Else, it will be the javascript trigger to "noMoreTikets()" that will land in the "dynamicDiv".