[WordPress] Saving latitude and longitude coordinates as a transient.

1-save-coordinates.php

<?php

// Assume the address is not encoded so make sure it's encoded for URLs
$address = urlencode( $address );

// Conact Google Map for the JSON result
$result = file_get_contents( "https://maps.googleapis.com/maps/api/geocode/json?address=$address&key=YOUR_API_KEY" );
$result = json_decode( $result );

// Grab the latitude and longitude of the city
$lat = $result->results[0]->geometry->location->lat;
$lng = $result->results[0]->geometry->location->lng;

// Encode the address and store it in the addresses
$cities_to_map[] = array(
    'adddress' => $address,
    'latlong'  => $lat . ',' . $lng,
    'id'       => $firm_id
);

// Store the values for 12 hours
set_transient( 'cities_to_map', $cities_to_map, 60 * 60 * 12 );

2-get-address-transient.php

<?php

// Retrieve the addresses from the transient data
$stored_addresses = get_transient( 'cities_to_map' );

// If the transient doesn't exist, contact the Maps API
if ( FALSE === $stored_addresses ) {

  // Assume the address is not encoded so make sure it's encoded for URLs
  $address = urlencode( $address );

  // Conact Google Map for the JSON result
  $result = file_get_contents( "https://maps.googleapis.com/maps/api/geocode/json?address=$address&key=YOUR_API_KEY" );
  $result = json_decode( $result );

  // Grab the latitude and longitude of the city
  $lat = $result->results[0]->geometry->location->lat;
  $lng = $result->results[0]->geometry->location->lng;

  // Encode the address and store it in the addresses
  $cities_to_map[] = array(
      'adddress' => $address,
      'latlong'  => $lat . ',' . $lng,
      'id'       => $firm_id
  );

  // Store the values for 12 hours
  set_transient( 'cities_to_map', 60 * 60 * 12 );
  
}

Say I have an array of 'london, newcastle, zimbabwe' – how would you approach saving this as a transient you can use, doesn't this work as only a single address as it is?