In Advanced Custom Fields: Which function can I use to get the full meta key of a field by its field key?

So, if I have a field with the name some_field and the field key field_sd54hfs5df: How do I get the name by the key?

I found the function acf_get_fields() and acf_get_field(), but when using field types like group, flexibel_content or repeater the names in the returned arrays are not the full names that are stored in the meta database tables.

For example, when a group has the name some_group and the field some_field the mentioned functions only return some_group or some_field, but not the full meta_key, which is some_group_some_field.

Unfortunately subfields of such a field type are not returned, so I don't see an option to reformat the returned arrays to combine the arrays recursively to built up the full meta key names.

I have written the below method to fetch the field name as stored under the _some-field… metadata by ACF, but when working in an environment with trash metadata and old records this is fetching multiple records, so that isn't a solution.

 * Get a meta key name by a ACF field key
 * @since 1.0.22
 * @param string $key
 * @return null|string
public function getUserMetaKey(string $key): ?string
    global $wpdb;
    $select = "SELECT distinct meta_key FROM $wpdb->usermeta WHERE meta_value = '$key' AND meta_key NOT LIKE 'acfe_form_actions_%'";
    // Debug::log($select);
    $usermeta = $wpdb->get_results($select);
    // Debug::log($usermeta);
    if (count($usermeta) > 0) {
        $metaKey = $usermeta[0]->meta_key;
        $metaKey = ltrim($metaKey, '_');
        return $metaKey;
    return null;

1 Answer 1


There's a few ways to achieve this but here's one which supports an unknown depth of children, for example where you have nested groups within groups.

Given the field key "field_{some_hash}" of the field, this function will retrieve the field, and its parent most field, and so on until we reach the top of the field tree.

function custom_acf_get_field_name_by_key( $key ) {

    $field = acf_maybe_get_field( $key );

    if ( empty( $field ) || ! isset( $field['parent'], $field['name'] ) ) {
        return $field;

    $ancestors = array();

    while ( ! empty( $field['parent'] ) && ! in_array( $field['name'], $ancestors ) ) {

        $parent = acf_get_field( $field['parent'] );

        $ancestors[] = $field['name'];

        $field = $parent;


    $formatted_key = array_reverse( $ancestors );
    $formatted_key = implode( '_', $formatted_key );

    return "_$formatted_key";


Assume a case where I have a nested group:

 - dev_group_test | field_61ecf308ded3e | group
   ∟ title        | field_61ecf316ded3f | text
   ∟ location     | field_61ecf31cded40 | text
   ∟ sub_group    | field_61ecfa1fe5894 | group
     ∟ sub_group_title | field_61ecfa2de5895 | text

If I want the full key of sub_group_title:

$meta_key = custom_acf_get_field_name_by_key( 'field_61ecfa2de5895' );
// result = _dev_group_test_sub_group_sub_group_title

If I want the full key of location:

$meta_key = custom_acf_get_field_name_by_key( 'field_61ecf31cded40' );
// result = _dev_group_test_location

NOTE: there may be more efficient ways to do this

  • 1
    Legendary, thank you so much! Note that in the while-loop, $field['parent'] > 0 doesn't seem to work for me, but !empty($field['parent']) does the job.
    – David Wolf
    Jan 23 at 9:38
  • @user1134827 You're welcome. I slapped it together quickly so maybe there is an edge case bug there, does your debug.log throw any warnings/errors? $field['parent'] > 0 is probably not needed anyway, I think, because IIRC every field returns a parent include the top most field, i.e. it always belongs to a parent post object that is stored in the *_posts table. So you can probably do away with that.
    – Adam
    Jan 23 at 9:43
  • 1
    Really appreciate it 🙏. debug.log is empty. Seems like when using $field['parent'] > 0 I got a blank _ (only 1 underscore), removing the condition returns a __foo_bar (2 underscores + field name) and using the !empty($field['parent']) returns _foo_bar (1 underscore + field name).
    – David Wolf
    Jan 23 at 9:59

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