无法通过AJAX请求运行SQL查询，使用相同类型的AJAX查询，除此之外的其他地方都可以正常工作

Question

I'm using this AJAX call everywhere else and it works like a charm but only this gives problem. I don't understand what is the problem? Why I'm getting "Error retried record:" still I don't see any problem and so easy.

PS: I echoed the values at AJAX side response and getting all three values there but database gives problem. More, same SQL query works fine at database side but when it deals with AJAX and PHP, it gives problem.

Values passed fine:

id1=get-version&id2=machine055&id3=vmlab

Database query seems fine:

SELECT `version` FROM `table1` where `machine` = 'machine055'

PHP+UI:

serverChange.on('change', function(){
            $("#progress").show();
            var selectedServer = $(this).val();

            $.ajax({
                type: "POST",
                url: "/web/scripts.php",
                data: { id1: "get-version", id2: selectedServer, id3: "vmlab" },
                success:function(msg){
                    $("#progress").hide();
                    alert(msg);
                }
            });

        });

PHP+Ajax:

if ($_POST['id1'] == "get-version" && $_POST['id3'] == "vmlab") {

    $conn = mysqli_connect("localhost", "root", "pwd", "db");
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }

    $sql = "SELECT `version` FROM `table1` where `machine` = '" .trim($_POST['id2']). "'";
    if ($conn->query($sql) === TRUE) {
        echo "Machine retrieved successfully.";
    } else {
        echo "Error retried record: " . $conn->error;
    }

Answer 1

I tried different approach and its working fine so not exploring much, here is the solution:

    $conn = mysqli_connect("localhost", "root", "pwd", "db");
     if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }

    $sql = "SELECT `version` FROM `table1` where `machine` = '" .trim($_POST['id2']). "'";
    $result = mysqli_query($conn, $sql);

    while($row =  mysqli_fetch_array($result)) {
        $rows[] = $row['version'];
    }

    echo ($rows[0]);

    $conn->close();

Thanks all for reading the issue and resolution.