Store locator with Advanced Custom Fields

get_stores_by_location.php

<?php 

function mbn_get_stores_by_location( $zip, $radius ) {
    global $wpdb;
    $radius = intval( $radius );

    // we first need to get the source coordinates
    $sql = "SELECT `latitude`, `longitude` FROM `wp_zip_codes` WHERE `zipcode` = '%s'";
    $coords = $wpdb->get_row( $wpdb->prepare( $sql, $zip ) );
    
    // now we'll get the other ZIP codes within the radius, ordered by distance
    $sql = "SELECT wp_zip_codes.zipcode, ( 3959 * acos( cos( radians( $coords->latitude ) ) * cos( radians( wp_zip_codes.latitude ) ) * cos( radians( wp_zip_codes.longitude ) - radians( $coords->longitude ) ) + sin( radians( $coords->latitude ) ) * sin( radians( wp_zip_codes.latitude ) ) ) )  AS distance FROM wp_zip_codes HAVING distance <= $radius OR distance IS NULL ORDER BY distance";

    $nearby_zips = $wpdb->get_results( $sql );

    // Store the zips in order to build the meta query
    $target_zips = array();
    foreach ($nearby_zips as $nearby_zip) :
        array_push($target_zips, $nearby_zip->zipcode);
    endforeach;

    // we're going to store the results as we go
    $store_results = array();

    if ( count( $target_zips > 0 ) ) :
        $args = array(
            'post_type' => 'retail-store',
            'posts_per_page' => 24,
            'meta_query' => array(
                array(
                    'key'     => 'zip',
                    'value'   => $target_zips,
                    'compare' => 'IN',
                ),
            ),
        );

        $store_query = new WP_Query($args);
        if ( $store_query->have_posts() ) : while ( $store_query->have_posts() ) :
            $store_query->the_post();
            $store_data = array();
            $store_data['id'] = get_the_ID();
            $store_data['name'] = get_the_title();
            $store_data['street_address'] = get_field('street_address');
            $store_data['street_address_2'] = get_field('street_address');
            $store_data['city'] = get_field('city');
            $store_data['state'] = get_field('state');
            $store_data['zip'] = get_field('zip');
            $store_data['telephone'] = get_field('telephone');
            $store_data['website'] = get_field('website');

            foreach ($nearby_zips as $nearby_zip) :
              if( $store_data['zip'] == $nearby_zip->zipcode ) :
                $store_data['distance'] = intval( $nearby_zip->distance );
              endif;
            endforeach;

            array_push( $store_results, $store_data );
            unset( $store_data );
        endwhile; endif;
        usort( $store_results, "mbn_cmp" );
    endif;
    return $store_results;
    wp_reset_postdata();
}

rg_store_publish.php

<?php 
function rg_store_publish() {
    global $post;
    $lat = get_post_meta($post->ID, 'lat', true);
    if ( empty($lat) ) : 
        $address = urlencode(get_field('street_address') ) . '+' . urlencode(get_field('city') ) . ',+' . urlencode(get_field('state') ) . ',+' . urlencode(get_field('zip') );
        $geocode_request = 'https://maps.googleapis.com/maps/api/geocode/json?address=' . $address;
        $response = wp_remote_get( $geocode_request );
        $obj = json_decode($response['body'], true);
        $location = $obj["results"][0]['geometry']['location'];
        update_post_meta($post->ID, 'lat', $location['lat']);
        update_post_meta($post->ID, 'lng', $location['lng']);
    endif;
}

add_action( 'publish_retail-store',  'rg_store_publish', 10, 2 );

Based on Jonathan Christopher's post here: https://mondaybynoon.com/store-locator-wordpress-pods/