MySQL get data from a query result - php

Question

I am a newbie to PHP and MySQL development. I have built an app in Cordova using Visual Studio. The app works in the following way:
User selects a serial number from a drop down
After selecting a serial number, the data is showed on the chart
There is a toggle switch in the app, through which i am inserting the on or off state in the database based on the serial number
What I want to do?
When a user select any serial number, the switch will show the last ON or Off state based on Command Name of that particular serial number.
For this, I have generated a msql query and this query shows me the last command name of selected serial number
Below is my PHP code:
<?php
require_once('config.php');
$dsn = $_REQUEST['Device_Serial_Number'];
$cmd_Name = $_REQUEST['Command_Name'];
$sqlFet = "select ADC.Server_Device_Command_ID , ADC.Device_ID ,
ADC.Server_Command_ID as Server_Command_ID, ASD.Command_Name
from ADS_Server_Device_Command ADC
inner join ADS_Server_Command ASD on adc.Server_Command_ID = asd.Server_Command_ID
inner join ADS_Device dsn on adc.Device_ID = dsn.Device_ID
where dsn.Device_Serial_Number = '$dsn'
order by adc.Server_Device_Command_ID desc LIMIT 1";
$result = mysqli_query($con,$sqlFet);
mysqli_close($con);
echo $cmd_Name;
?>
Below is my AJAX call in JavaScript:
$.ajax({
method: "GET",
url: "http://localhost:MyPort/server/toggleFetch.php",
data: { Command_Name: tData , Device_Serial_Number: selectedVal },
success: function (data) {
var dt = data;
if (dt.Command_Name == "On") {
$("#cmn-toggle-7").prop('checked', true);
}
else if (dt.Command_Name == "Off") {
console.log('else');
$("#cmn-toggle-7").prop('checked', false);
}
},
error: function (xhr, status, error) {
alert(xhr.responseText, status, error);
//toastr.success('Data not fetched', '', { timeOut: 2000 })
//alert('Error');
}
});
But it doesn't show the required result and gives error as shown in below image:
Updated Code:
Bellow is my php updated code
require_once('config.php');
$dsn = $_REQUEST['Device_Serial_Number'];
//$cmd_Name = $_REQUEST['Command_Name'];
$sqlFet = "select ADC.Server_Device_Command_ID , ADC.Device_ID ,
ADC.Server_Command_ID as Server_Command_ID, ASD.Command_Name
from ADS_Server_Device_Command ADC
inner join ADS_Server_Command ASD on adc.Server_Command_ID = asd.Server_Command_ID
inner join ADS_Device dsn on adc.Device_ID = dsn.Device_ID
where dsn.Device_Serial_Number = '$dsn'
order by adc.Server_Device_Command_ID desc LIMIT 1";
$result = mysqli_query($con,$sqlFet);
$row = mysqli_fetch_array($result, MYSQLI_BOTH);
mysqli_close($con);
echo $row["Command_Name"];
Bellow is the ajax
$.ajax({
method: "GET",
url: "http://localhost:MyPort/server/toggleFetch.php",
//dataType: "json",
data: { Command_Name: tData , Device_Serial_Number: selectedVal },
success: function (data) {
var dt = data;
if (dt == "On") {
$("#cmn-toggle-7").prop('checked', true);
}
else if (dt == "Off") {
console.log('else');
$("#cmn-toggle-7").prop('checked', false);
}
},
error: function (xhr, status, error) {
alert(xhr.responseText, status, error);
//toastr.success('Data not fetched', '', { timeOut: 2000 })
//alert('Error');
}
});
Now when running the code i am not getting any error but still i am not getting my required result i.e. the toggle doesn't change it's state
For more information please see the image bellow
I don't know what's the problem, any help would be highly appreciated.

Answer 1

This error means, that AJAX didnt send Command_Name via GET. You will have to check variable tData if it contains some value.

Answer 2

First step: dont send command_name with AJAX to PHP script (This causes Error on Line 5!!), it is not needed. Second step: in Php script you will have to change echo $command_name, to echo result from DB based on $dsn. So echo result from DB.
$row = mysqli_fetch_array($result, MYSQLI_BOTH);
echo $row["Command_name"]; //This should show ON/OFF state from DB to AJAX.