Untitled

<?php
$servername = "localhost";
$username = "root";
$pass = "bakalauras";
$dbname = "device_maintenance";
$conn = mysqli_connect($servername, $username, $pass, $dbname);
?>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
    $(document).ready(function(){
            $('#devName').on('change', function(e){
                var id = e.target.value;
                $.ajax({
                type: "POST",
                url: 'Ajax_error_form.php',
                data: ({ id: id}),
                success: function(data) {    //alert(data);
                    alert(data);
                }
                });
            })
            });
</script>
</head>
<body>
    <p>Add Error Codes</p>
    <form>
    Choose a device:
        <br>
    <?php $selectDevices="SELECT * FROM inventory_1";
        $resultSelectDevices=mysqli_query($conn,$selectDevices);
        echo "<select name=\"device_name\" id=\"devName\">";
        echo "<option size =30 ></option>";
        echo "<option selected = 'selected' disabled = 'disabled'>Device for Fullfilment</option>";
        $devID = $_POST['device_name'];
        while($row = mysqli_fetch_array($resultSelectDevices)) {
            echo "<option value='".$row['ID']."' placeholder = 'Choose a device'>".$row['device_name']."</option>";
        }
            echo "</select>"; ?>
        <br>
    </form>

    <div id="1parts"></div>


</body>
</html>

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Ajax_error_form.php


<?php
$devID = $_POST['id'];
$servername = "localhost";
$username = "root";
$pass = "bakalauras";
$dbname = "device_maintenance";
$conn = mysqli_connect($servername, $username, $pass, $dbname);
$sqlDevpart = "SELECT inventory_1.ID FROM inventory_parts_seconds INNER JOIN inventory_1 ON inventory_1.ID = inventory_parts_seconds.device_ID WHERE inventory_1.ID = ".$devID." ";
$result = mysqli_query($conn, $sqlDevpart);
$row = mysqli_fetch_assoc($result);
echo $row['ID'];
?>