how to fetch the meta field keys/meta boxes from a post type?

Question

get_post_custom will return all the meta_key => meta_value pairs for a given post. It returns the fields in sort of a weird format, however.

eg.

<?php
$meta = get_post_custom(1);

/*
$meta would be...

arrary(
   'some_meta_key' => array(
       'one_meta_value'
   )
);
*/

Unless you mean get all meta for all posts in a given post type, for that you’ll need a custom query.

<?php
function wpse65225_get_all_meta($type)
{
    global $wpdb;

    $res = $wpdb->get_results($wpdb->prepare(
        "SELECT post_id, meta_key, meta_value FROM {$wpdb->postmeta} WHERE post_id IN
        (SELECT ID FROM {$wpdb->posts} WHERE post_type = %s)", $type
    ), ARRAY_A);

    return $res;
}