无法将谷歌地图生成的信息导入MySQL

I am trying to insert values for longitude, latitude and descriptions of locations generated from google maps (the ID value is to be generated within PhpMyAdmin. When I run the following code I always get the "error" message. If I "echo $sql;" before //insert values into database then I get the intended output so I guess it must be a problem with transferring to the database.

I'm using phpMyAdmin from within MAMP so am not sure if that is causing any issues of whether I'm missing something obvious in the code? I'm fairly new to PHP so may have missed something obvious! Any help would be much appreciated.

<?php

$con=mysqli_connect("localhost", "root", "root", "googlemaps") or die("could not connent to db");
error_reporting(0);

for($i=0;$i<count($_POST['value']);$i=$i+3)
{
    $sql .= "(NULL, '".$_POST['value'][$i]."', '".$_POST['value'][$i+1]."', '".$_POST['value'][$i+2]."'),";
}

//remove last comma
$sql = substr($sql,0,-1);


//insert values into database
$query = "INSERT INTO 'googlemaps'.'values' ('id', 'lat', 'lng', 'des') VALUES " .$sql;

$status = mysqli_query($con, $query);

if($status)
    echo "inserted";
else
    echo "error";

?>