File attachment VIA Form API

attachment.php

function wj_profile_photo_upload_form() {
  $form = array();

  $instance = field_info_instance('profile2', 'field_photo', 'profile');
  $field = field_info_field('field_photo');

  $form['profile_field_photo'] = array(
    '#type' => 'managed_file',
    '#upload_location' => file_field_widget_uri($field, $instance),
    '#upload_validators' => file_field_widget_upload_validators($field, $instance),
    '#value_callback' => 'file_field_widget_value',
  );

  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Upload'),
    '#id' => 'wj-profile-photo-upload',
  );

  $form['#attributes']['enctype'] = "multipart/form-data";
  return $form;
}

function wj_profile_photo_upload_form_submit($form, &$form_state) {
  if ($fid = $form_state['values']['profile_field_photo']) {
    db_update('file_managed')->fields(array('status' => 1))->condition('fid', $fid)->execute();
  }
}