How check how many custom fields has a Wordpress post?

Question

如何检查有多少个自定义字段有帖子，我不想检索任何值，但我需要找出有多少个自定义字段有帖子。

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