Submit Multi-Dimensional Array to mySQL - php

Question

I have a mySQL table with the fields:
preview_url
large_url
And I have an object that I submit with the following structure:
var $urls = {largeImg:[],preview:[]}
$urls.largeImg values have to be inserted into 'large_url' and
$urls.preview_url values have to be inserted into 'preview_url'
$urls.largeImg[0] has to go in the same mysql table row as $urls.preview[0],
$urls.largeImg[1] into the same row as $urls.preview[1] and so on.
my php:
$urls = $_POST['urls'];
function cache_urls($urls){
global $db;
foreach($urls as $url){
$sql = "INSERT INTO cache ";
$sql .= "(preview_url, large_url) ";
$sql .= "VALUES (";
$sql .= "'" . db_escape($db, $url['preview']) . "', ";
$sql .= "'" . db_escape($db, $url['largeImg']) . "'";
$sql .= ");";
$result = mysqli_query($db, $sql);
}
And then I also tried this:
foreach($urls as $url){
foreach($url as $key => $value){
$sql = "INSERT INTO cache ";
$sql .= "(preview_url, large_url) ";
$sql .= "VALUES (";
if($key==="preview"){
$sql .= "'" . db_escape($db, $value) . "', ";
}
if($key==="largeImg"){
$sql .= "'" . db_escape($db, $value) . "'";
}
$sql .= ");";
$result = mysqli_query($db, $sql);
}
}
So I assume the SQL bit must be wrong but I'm really at the end of my knowledge! Any help much appreciated.

Answer 1

You should do it like this way,
$sql = "INSERT INTO cache (preview_url, large_url) values";
foreach($urls["largeImg"] as $index => $large_url){
$preview_url = $urls["preview"][$index];
$sql .= "('" . db_escape($db,$preview_url) . "','" . db_escape($db,$large_url) . "'),";
}
$sql = rtrim($sql,",");