Field API

Attach custom data fields to Drupal entities.

The Field API allows custom data fields to be attached to Drupal entities and takes care of storing, loading, editing, and rendering field data. Any entity type (node, user, etc.) can use the Field API to make itself "fieldable" and thus allow fields to be attached to it. Other modules can provide a user interface for managing custom fields via a web browser as well as a wide and flexible variety of data type, form element, and display format capabilities.

The Field API defines two primary data structures, Field and Instance, and the concept of a Bundle. A Field defines a particular type of data that can be attached to entities. A Field Instance is a Field attached to a single Bundle. A Bundle is a set of fields that are treated as a group by the Field Attach API and is related to a single fieldable entity type.

For example, suppose a site administrator wants Article nodes to have a subtitle and photo. Using the Field API or Field UI module, the administrator creates a field named 'subtitle' of type 'text' and a field named 'photo' of type 'image'. The administrator (again, via a UI) creates two Field Instances, one attaching the field 'subtitle' to the 'node' bundle 'article' and one attaching the field 'photo' to the 'node' bundle 'article'. When the node system uses the Field Attach API to load all fields for an Article node, it passes the node's entity type (which is 'node') and content type (which is 'article') as the node's bundle. field_attach_load() then loads the 'subtitle' and 'photo' fields because they are both attached to the 'node' bundle 'article'.

Field definitions are represented as an array of key/value pairs.

array $field:

• id (integer, read-only): The primary identifier of the field. It is assigned automatically by field_create_field().
• field_name (string): The name of the field. Each field name is unique within Field API. When a field is attached to an entity, the field's data is stored in $entity->$field_name. Maximum length is 32 characters.
• type (string): The type of the field, such as 'text' or 'image'. Field types are defined by modules that implement hook_field_info().
• entity_types (array): The array of entity types that can hold instances of this field. If empty or not specified, the field can have instances in any entity type.
• cardinality (integer): The number of values the field can hold. Legal values are any positive integer or FIELD_CARDINALITY_UNLIMITED.
• translatable (integer): Whether the field is translatable.
• locked (integer): Whether or not the field is available for editing. If TRUE, users can't change field settings or create new instances of the field in the UI. Defaults to FALSE.
• module (string, read-only): The name of the module that implements the field type.
• active (integer, read-only): TRUE if the module that implements the field type is currently enabled, FALSE otherwise.
• deleted (integer, read-only): TRUE if this field has been deleted, FALSE otherwise. Deleted fields are ignored by the Field Attach API. This property exists because fields can be marked for deletion but only actually destroyed by a separate garbage-collection process.
• columns (array, read-only): An array of the Field API columns used to store each value of this field. The column list may depend on field settings; it is not constant per field type. Field API column specifications are exactly like Schema API column specifications but, depending on the field storage module in use, the name of the column may not represent an actual column in an SQL database.
• indexes (array): An array of indexes on data columns, using the same definition format as Schema API index specifications. Only columns that appear in the 'columns' setting are allowed. Note that field types can specify default indexes, which can be modified or added to when creating a field.
• foreign keys: (optional) An associative array of relations, using the same structure as the 'foreign keys' definition of hook_schema(). Note, however, that the field data is not necessarily stored in SQL. Also, the possible usage is limited, as you cannot specify another field as related, only existing SQL tables, such as filter formats.
• settings (array): A sub-array of key/value pairs of field-type-specific settings. Each field type module defines and documents its own field settings.
• storage (array): A sub-array of key/value pairs identifying the storage backend to use for the for the field:
  • type (string): The storage backend used by the field. Storage backends are defined by modules that implement hook_field_storage_info().
  • module (string, read-only): The name of the module that implements the storage backend.
  • active (integer, read-only): TRUE if the module that implements the storage backend is currently enabled, FALSE otherwise.
  • settings (array): A sub-array of key/value pairs of settings. Each storage backend defines and documents its own settings.

Field instance definitions are represented as an array of key/value pairs.

array $instance:

• id (integer, read-only): The primary identifier of this field instance. It is assigned automatically by field_create_instance().
• field_id (integer, read-only): The foreign key of the field attached to the bundle by this instance. It is populated automatically by field_create_instance().
• field_name (string): The name of the field attached to the bundle by this instance.
• entity_type (string): The name of the entity type the instance is attached to.
• bundle (string): The name of the bundle that the field is attached to.
• label (string): A human-readable label for the field when used with this bundle. For example, the label will be the title of Form API elements for this instance.
• description (string): A human-readable description for the field when used with this bundle. For example, the description will be the help text of Form API elements for this instance.
• required (integer): TRUE if a value for this field is required when used with this bundle, FALSE otherwise. Currently, required-ness is only enforced during Form API operations, not by field_attach_load(), field_attach_insert(), or field_attach_update().
• default_value_function (string): The name of the function, if any, that will provide a default value.
• default_value (array): If default_value_function is not set, then fixed values can be provided.
• deleted (integer, read-only): TRUE if this instance has been deleted, FALSE otherwise. Deleted instances are ignored by the Field Attach API. This property exists because instances can be marked for deletion but only actually destroyed by a separate garbage-collection process.
• settings (array): A sub-array of key/value pairs of field-type-specific instance settings. Each field type module defines and documents its own instance settings.
• widget (array): A sub-array of key/value pairs identifying the Form API input widget for the field when used by this bundle:
  • type (string): The type of the widget, such as text_textfield. Widget types are defined by modules that implement hook_field_widget_info().
  • settings (array): A sub-array of key/value pairs of widget-type-specific settings. Each field widget type module defines and documents its own widget settings.
  • weight (float): The weight of the widget relative to the other elements in entity edit forms.
  • module (string, read-only): The name of the module that implements the widget type.
• display (array): A sub-array of key/value pairs identifying the way field values should be displayed in each of the entity type's view modes, plus the 'default' mode. For each view mode, Field UI lets site administrators define whether they want to use a dedicated set of display options or the 'default' options to reduce the number of displays to maintain as they add new fields. For nodes, on a fresh install, only the 'teaser' view mode is configured to use custom display options, all other view modes defined use the 'default' options by default. When programmatically adding field instances on nodes, it is therefore recommended to at least specify display options for 'default' and 'teaser':
  • default (array): A sub-array of key/value pairs describing the display options to be used when the field is being displayed in view modes that are not configured to use dedicated display options:
    • label (string): Position of the label. 'inline', 'above' and 'hidden' are the values recognized by the default 'field' theme implementation.
    • type (string): The type of the display formatter, or 'hidden' for no display.
    • settings (array): A sub-array of key/value pairs of display options specific to the formatter.
    • weight (float): The weight of the field relative to the other entity components displayed in this view mode.
    • module (string, read-only): The name of the module which implements the display formatter.
  • some_mode: A sub-array of key/value pairs describing the display options to be used when the field is being displayed in the 'some_mode' view mode. Those options will only be actually applied at run time if the view mode is not configured to use default settings for this bundle:
    • ...
  • other_mode:
    • ...

The (default) render arrays produced for field instances are documented at field_attach_view().

Bundles are represented by two strings, an entity type and a bundle name.

• Field Types API. Defines field types, widget types, and display formatters. Field modules use this API to provide field types like Text and Node Reference along with the associated form elements and display formatters.

• Field CRUD API. Create, updates, and deletes fields, bundles (a.k.a. "content types"), and instances. Modules use this API, often in hook_install(), to create custom data structures.

• Field Attach API. Connects entity types to the Field API. Field Attach API functions load, store, generate Form API structures, display, and perform a variety of other functions for field data connected to individual entities. Fieldable entity types like node and user use this API to make themselves fieldable.

• Field Info API. Exposes information about all fields, instances, widgets, and related information defined by or with the Field API.

• Field Storage API. Provides a pluggable back-end storage system for actual field data. The default implementation, field_sql_storage.module, stores field data in the local SQL database.

• Field API bulk data deletion. Cleans up after bulk deletion operations such as field_delete_field() and field_delete_instance().

• Field language API. Provides native multilingual support for the Field API.

File

modules/field/field.module, line 27

Functions

Constants

Classes