$("#append").click(function (e) {
    e.preventDefault();
    var textboxes = $(".textbox").length;
        $(".inc").append("<div class='controls'><input class='textbox form-control' type='text' name='textbox[]'><input class='textbox form-control' type='text' name='box[]' ><input class='textbox form-control' type='text' name='box1[]' ><input class='textbox form-control' type='text' name='box2[]' ><a href='#' class='remove_this btn btn-danger'>remove</a> </div>");
});

$(document).on('click', '.remove_this', function (e) {
    e.preventDefault();
    $(this).parent().remove();
});

<form class="form-horizontal" method= "POST">
<div class="control-group">
    <div class="inc">
        <div class="controls">
            <button style="margin-left: 50px" class="btn btn-info" type="submit" id="append" name="append">
            Add Textbox</button>
            <br>
            <br>
        </div>
    </div>
    <input type="submit" class="btn btn-info" name="submit" value="submit"/>
</div>

$host = "localhost";
$dbname = "lala";
$user = "root";
$pass = "";
$conn = new PDO("mysql:host=$host; dbname=$dbname", $user, $pass);
if (isset($_POST['submit'])) {
$textboxes = $_POST['textbox'];
$textboxes1 = $_POST['box1'];
$textboxes2 = $_POST['box2'];
$boxes = $_POST['box'];
$x=0;
$a=0;
$z=0;

    foreach ($textboxes as $textbox ) {
 $y=0;
            if($y==$x){
                foreach ($boxes as $box ) {
                    if($z==$y){
                        foreach ($textboxes1 as $box1 ) {

                            if($a==$z){
                                foreach ($textboxes as $box2 ) {
                                    if($y==$x){

                                        $sql = "INSERT into sasa (sasa,sasa1,sasa2,sasa3) values('$textbox','$box','$box1','$box2')";
                                        echo $sql . "<br>";
                                        $q = $conn->query($sql);
                                    }
                                    $x++;
                                    $y++;

                                }
                            }
                            $a++;
                        }
                    }
                    $z++;
                }
            }


    }

}