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Cloning fields

The clone feature of Meta Box allows you to create multiple inputs from a text, textarea, select, ... fields without declaring many fields in the code. Combining the clone feature with groups gives you a flexible way to define repeatable content.

Clone is a feature

The difference between Meta Box and other plugins is that the clone feature can be applied to all field types. And it's a feature, not a field type. Then, every field or group can be cloneable or repeater. They are called cloneable fields or cloneable groups.

Making a field cloneable

When editing a field, turn on this Cloneable option in the settings of the field:

enable clone feature

After turning in the Cloneable option, other clone settings will appear.

other clone settings

Not a premium user?

You can see the settings visually as above since this instruction uses Meta Box Builder extension, which is a premium extension providing the UI to create fields, and is already bundled in Meta Box AIO and MB Core. If you're not a premium user, please purchase a license to use it. However, you can do this with code.

No matter what you are using the UI or code, this is a brief description of the clone settings. The keys are for reference in code.

SettingsKeyDescription
CloneablecloneMake the field cloneable? true or false (default). Optional.
Sortablesort_cloneAllow to drag-and-drop sort clones. true or false (default).
Clone default valueclone_defaultClone the default value of the field? true or false (default).
Clone as multipleclone_as_multipleWhether to store cloned values in multiple rows in the database
Max number of clonesmax_cloneLimit the number of clones. Must be greater than 2. Optional.
Min number of clonesmin_cloneMinimum number of clones. Optional.
Add more textadd_buttonThe text for Add more clone button. Optional. Default "+ Add more".

After saving the field group, in the post editor, you'll see an + Add more button below the field input. Clicking it allows you to enter more values:

view clones in action

If you're a developer and want to use code, then you need to add the clone settings into the field settings:

add_filter( 'rwmb_meta_boxes', function ( $meta_boxes ) {
$meta_boxes[] = [
'title' => 'Event details',
'post_types' => 'event',
'fields' => [
[
'name' => 'Date and time',
'id' => 'datetime',
'type' => 'datetime',
'clone' => true,
// Other clone settings
],
[
'name' => 'Location',
'id' => 'location',
'type' => 'text',
],
[
'name' => 'Map',
'id' => 'map',
'type' => 'osm',
'address_field' => 'location',
],
],
];

return $meta_boxes;
} );

Data of cloneable fields

For cloneable fields, values are stored as a serialized array in a single row in the database, unless you set 'clone_as_multiple' => true.

Using serialized data has some benefits:

  • Works for all field types, including nested groups.
  • Works perfectly with the helper function or with WordPress's get_post_meta function (WordPress automatically deserializes string and returns an array).
  • Reduces the database size (number of rows), especially when you have nested groups of many fields.

Query posts by cloneable fields

By default, cloned values are stored as a serialized array, which doesn't allow you to query posts by these values. For example, if you have a cloneable field start_date for the event post type, and you want to query events in May 2019 like this:

$args = [
'post_type' => 'event',
'meta_query' => [
[
'key' => 'start_date', // This field is cloneable
'value' => ['2019-05-01', '2019-05-31']
'compare' => 'BETWEEN',
],
],
];
$query = new WP_Query( $args );

Then it doesn't work.

To solve this problem, you need to enable the Clone as multiple settings for the field.

Enable the Clone as multiple settings

With that, Meta Box will save cloneable values in multiple rows in the database, where each row contains one value. That means if start_date has 2 values ['2019-05-01', '2019-04-30'], it will be saved in 2 rows in the database, one for 2019-05-01 and one for 2019-04-30. The data is not serialized anymore. And thus, your above query will work!

Default values

When making a field to be cloneable, its data is an array of cloned values. So, the std parameter (default value) should represent this structure, e.g. array of cloned values.

add_filter( 'rwmb_meta_boxes', function ( $meta_boxes ) {
$meta_boxes[] = [
'title' => 'Event details',
'post_types' => 'event',
'fields' => [
[
'name' => 'Date and time',
'id' => 'datetime',
'type' => 'datetime',
'clone' => true,
'std' => [
'2022-04-20',
'2022-04-21',
],
],
[
'name' => 'Location',
'id' => 'location',
'type' => 'text',
],
[
'name' => 'Map',
'id' => 'map',
'type' => 'osm',
'address_field' => 'location',
],
],
];

return $meta_boxes;
} );