The hidden field creates a simple hidden input. It’s usually used to store custom data that cannot be changed.
This field doesn’t have any specific settings. It only uses common field settings.
To store the hidden value, put it in the
array( 'id' => 'field_id', 'type' => 'hidden', // Hidden field must have predefined value 'std' => 'Hidden value', ),
Although the value is fixed in the code, this field still saves it in the post meta.
To get the field value, use this code
$value = rwmb_meta( $field_id ); echo $value;
Read more about rwmb_meta().