Popup on if statement in php - php

Question

I have a html form which looks like this:
<form action="submitOrder.php" method="get">
<select name="orderForm">
<?php
echo '<option value=" "> </option>';
while($row = \mssql_fetch_array($employeeOrderResult))
{
echo '<option value="'.$row[EMPLOYEE].'">'.$row[EMPLOYEE].'</option>';
}
?>
<option value="Gæst">Gæst</option>
<option value="Praktikant-01">Praktikant-01</option>
<option value="Praktikant-02">Praktikant-02</option>
<option value="Praktikant-03">Praktikant-03</option>
</select>
<br>
Vare: <input type ="text" name="varenr"><br>
Antal: <input type="text" name="antal"><br>
<input type="submit" value="Bestil">
</form>
It fetches som data from a database and adds some special guests.
Now, when it confirms it redirects to a page which has this code in it:
<?php
$ofAntal = $_GET['antal'];
$ofMedarbejder = $_GET['orderForm'];
$ofDato = date('Y-m-d H:i:s');
$ofVareNr = $_GET['varenr'];
$sql = "INSERT INTO Bestillinger(bestillingsAntal,medarbejder,dato,vareNr) VALUES('$ofAntal','$ofMedarbejder','$ofDato','$ofVareNr')";
$validation = mysql_query($sql, $MySQLcon);
if(!$validation)
{
die('Couldnt enter data ' . mysql_error());
}
echo 'Entered data succesfully';
?>
Now, I need a confirmation popup of some kind, if the amount (ofAntal) is above 1, and Ive looked into several solutions. The problem is i started working with PHP tuesday morning, and i cant find a solution that works for me.
All it has to do, is submit the data is yes is clicked, and cancel it if the user clicks no/cancel. This is ofc done in an IF statement, thats not the issue, the issue is how to implement it properly.
ANY help is highly appreciated :)

Answer 1

Use javascript confirm box on onclick attribute for submit button. It will give you yes and cancel options.
<input type="submit" value="Bestil" onclick="confirm("Are you sure ?");">
Orelse
You can write a function in javascript to check that
<input type="submit" value="Bestil" onclick="myfunct();">
function myfunct(){
if(document.getElementById("antal").value > 1)
confirm("Are you sure");
return true;
}