PHP Array Insert

The first array is $countries and the second array is $cities.

$map = array();
while (!empty($countries) && !empty($cities)) {
  $map[array_shift($countries)][] = array_shift($cities);
}

foreach ($map as $country => $cities) {
  $cities = join(', ', $cities);
  // TODO: insert row with $country and $cities into database.
}

As as side note, I suspect your database is not normalized. Read up on normalization of databases, if you have not already done so.

Have a read through this tutorial: http://www.tizag.com/mysqlTutorial/

If you reindex your arrays you can then iterate over both of them in parallel:

$cities = array_values($cities);
$countries = array_values($countries);
for($i = 0; $i < count($cities); ++$i) {
    $city = $cities[$i];
    $country = $countries[$i];

    // now do something with $city and $country
}

Now let's see what the "do something" part might be. If you want to concatenate city names by country, you need to group by country first. So let's do that:

$groups = array();

for (...) {
    $city = $cities[$i];
    $country = $countries[$i];

    if (!isset($groups[$country])) $groups[$country] = array();
    $groups[$country][] = $city;
}

At this point you should do a print_r($groups) to see that we have grouped the cities. Converting each group to a concatenated string is easy:

foreach($groups as &$group) { // ATTENTION: iterating by reference
    $group = implode(', ', $group);
}

And do a print_r again.

However, this type of database structure doesn't look right (depends on the application, so not definite). Perhaps you should consider having a table with country/city columns, so each pair of elements from the input arrays would correspond to a row.

1. You must binding country code with city like this:

   Array
   (
       [0]['code'] => UK
       [0]['city'] => London
   )
   ....
   

2. If you have multidimensional array with => pairs, you can create appropriate sql's using foreach and case (if) statements.

So I am not sure what you are trying to do or why you have two arrays for what should probably be 1, this is assuming of course that the city is always tied to its correct country. What I would do is say is Manchester and London are both in the UK so their country field in the database would be be UK, and then you could call them with a simple MySQL query asking for all the cities where the country is equal to the city code

So your database would look like this

 ID      CITY       COUNTRY
 1       London     UK
 2       Manchester UK
 3       New York   USA
 4       Florida    USA
 5       Hawaii     USA
 6       Paris      France

And then you can call it with a MySQL query just as you want,

 SELECT * FROM table WHERE country = 'UK'

This would then give you a result for London and Manchester

This should get you going in the right direction