Question

How to check how many custom fields has a post, I don’t want retrieve any value but I need to find out how many custom fields has a post.

Answer 1

<?php
    // get only the keys as you only need the number
    $cfields = get_post_custom_keys($post_id);
    // num_cfields will store the number of custom fields
    $num_cfields = count($cfields);
?>

There’s also get_post_custom as well as get_post_custom_values