function hook_field_presave in Drupal 7
Define custom presave behavior for this module's field types.
Make changes or additions to field values by altering the $items parameter by reference. There is no return value.
Parameters
$entity_type: The type of $entity.
$entity: The entity for the operation.
$field: The field structure for the operation.
$instance: The instance structure for $field on $entity's bundle.
$langcode: The language associated with $items.
$items: $entity->{$field['field_name']}[$langcode], or an empty array if unset.
Related topics
4 functions implement hook_field_presave()
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
- file_field_presave in modules/
file/ file.field.inc  - Implements hook_field_presave().
 - image_field_presave in modules/
image/ image.field.inc  - Implements hook_field_presave().
 - number_field_presave in modules/
field/ modules/ number/ number.module  - Implements hook_field_presave().
 - taxonomy_field_presave in modules/
taxonomy/ taxonomy.module  - Implements hook_field_presave().
 
1 invocation of hook_field_presave()
- field_attach_presave in modules/
field/ field.attach.inc  - Perform necessary operations just before fields data get saved.
 
File
- modules/
field/ field.api.php, line 436  - Hooks provided by the Field module.
 
Code
function hook_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) {
  if ($field['type'] == 'number_decimal') {
    // Let PHP round the value to ensure consistent behavior across storage
    // backends.
    foreach ($items as $delta => $item) {
      if (isset($item['value'])) {
        $items[$delta]['value'] = round($item['value'], $field['settings']['scale']);
      }
    }
  }
}