SyntaxError {stack: (...), message: "Unexpected token <"} tracker.js:41 parsererror - php

Question

I want to retrieve the data from db using PHP
$device_owner_resultset=mysqli_query($con, "SELECT * FROM `device_owner_details` WHERE `deviceId` =$device_details_data_id");
$device_owner_resultset_data = mysqli_fetch_array($device_owner_resultset);
$owner_deviceid = $device_owner_resultset_data['deviceId'];
$owner_name = $device_owner_resultset_data['name'];
$name_fetch_rows = mysqli_fetch_row($device_owner_resultset);
$device_realtime_resultset=mysqli_query($con, "SELECT * FROM `device_realtime_stats` WHERE `deviceId` = $owner_deviceid LIMIT $start_from , $limit");
$rows_fetch = mysqli_fetch_row($device_realtime_resultset);
if(($total_pages<=$page) &&( $total_pages>0))
{
$device_details=array('devices'=> array());
for($i=1;$i<=20;$i++)
{
$details =array('name' => $name_fetch_rows[$i]-> name, 'latitude' => $rows_fetch[$i] -> currentLatitude, 'longitude' => $rows_fetch[$i] -> currentLongitude);
array_push($device_details['devices'],$details);
}
$response = json_encode($device_details);
echo $response;
}
Here i have an parse error, what is the mistake from my coding , i think error is in mysqli_fetch_rows and its calling array

Answer 1

You are not using mysqli_fetch_row($result) correctly. The function mysqli_fetch_row($result) does not return all the row data. It returns an array of a single row as an enumerated array. Try this code using this code instead:
// Now only selects name column and added LIMIT 1 to MySQL query for efficiency
$device_owner_resultset = mysqli_query($con, "SELECT name FROM `device_owner_details` WHERE `deviceId` = $device_details_data_id LIMIT 1");
// Now using mysqli_fetch_assoc($result)
// instead of mysqli_fetch_array($result) for clarity
$device_owner_resultset_data = mysqli_fetch_assoc($device_owner_resultset);
// Got rid of $owner_deviceid because it should be the same as $device_details_data_id
$owner_name = $device_owner_resultset_data['name'];
// Got rid of $name_fetch_rows because it is redundant with $device_owner_resultset_data
// Query now specifies which columns it selects for clarity and efficiency
$device_realtime_resultset = mysqli_query($con, "SELECT currentLatitude, currentLongitude FROM `device_realtime_stats` WHERE `deviceId` = $device_details_data_id LIMIT $start_from, $limit");
if ($total_pages <= $page && $total_pages > 0) {
$device_details=array('devices'=> array());
// This loops through all the rows from the query
while ($row = mysqli_fetch_assoc($device_realtime_resultset)) {
// $row is an associative array where the column name is
// mapped to the column value.
// The owner name should remain the same because there is
// only one owner.
$details = array('name' => $owner_name,
'latitude' => $row["currentLatitude"],
'longitude' => $row["currentLongitude"]
);
array_push($device_details['devices'], $details);
}
$response = json_encode($device_details);
echo $response;
}
If the columns of the device_realtime_stats table are not named currentLatitude and currentLongitude make sure they are renamed.

Answer 2

$mysql_all_resultset = mysqli_query($con, " SELECT dot.name, drs.currentLatitude, drs.currentLongitude FROM device_details dt, device_owner_details dot, device_realtime_stats drs WHERE dt.vendorId=$vendor_id AND dot.deviceId=dt.id AND drs.deviceId= dot.deviceId LIMIT $start_from, $limit ");
if(($total_pages<=$page) &&( $total_pages>0))
{
$device_details=array('devices'=> array());
while ($rows_fetch = mysqli_fetch_assoc($mysql_all_resultset))
{
$details =array('name' => $rows_fetch['name'], 'latitude' => $rows_fetch['currentLatitude'], 'longitude' => $rows_fetch['currentLongitude']);
array_push($device_details['devices'],$details);
}
$response = json_encode($device_details);
echo $response;
}