php 7.1 error with book node edit, Illegal string offset 'weight' and Cannot create references to/from string offsets in drupal_array_set_nested_value() line 6781 /includes/common.inc

@cilefen switched the component from 'base system' to 'book.module'. I will not change that back, but I was uncertain what the problem really was and was not convinced that there was an actual problem with the book.module, but instead that PHP71 requires stronger or more accurate variable 'typing' that must be fixed in the general purpose function in common.inc, drupal_array_set_nested_value().

Since the problem goes away when switching back to PHP56 I thought perhaps there is no real problem in the 'book.module' but instead in the base system.

Okay sorry to raise the alarm. This problem is caused by the book_made_simple module. That module offers permission to hide the book weight field in order to simplify the UI for certain users. Apparently when doing this the book weight field does not then properly default.

I hope to look into this further and post back here and create an issue at book_made_simple once I figure out why this is the case and why it works in PHP56 and not in PHP71. It may still be that the drupal_array_set_nested_value() could be improved to handle cases when contrib modules do not properly initialize node variables.

I think it should be easily reproduced by anyone by installing book_made_simple and then visit the perms page and restrict the book_made_simple perm 'User will have all rights on books' from a user that has the right the create books. When this user then tries to edit/save a book the error will surface in PHP71 but not PHP56.

The foul play happens in book_made_simple.module in book_made_simple_form_alter() beginning line 240.

book_made_simple provides permissions to take 'Book Outline' off the book content edit form vertical tabs. So that means that information is not available on the book node edit submit. However, I am not sure what the Drupal solution is for this.

Who is the guilty party?

I guess if book_made_simple takes that off the form it ought to also provide proper defaults.

However, maybe Drupal core book.module could also be better prepared for this.

Certainly, Drupal core drupal_array_set_nested_value() should also be better prepared for this and protected from contrib modules.

Still trying to understand this better, especially why PHP56 and PHP71 makes a difference.

Okay, more info.

When book_made_simple enabled and is used to take 'Book Outline' off the book content edit form then book_made_simple_form_alter() is called and _book_add_form_elements() is NOT called from book.module. The _book_add_form_elements() function in book.module assigns two important defaults to the book content edit form which are then not assigned.

scratch that.

I viewed $form['book'] for the working and non-working case and the only difference is

working: $form[book][#type] => fieldset
non-working: $form[book][#type] => hidden

otherwise all the remaining element of $form[book] are the same.

oh, the non-working also includes an additional element $form[book][reorder], but that seems innocent enough

turning to devel next

I have the devel backtrace, but how do I copy that from the message area to here?

Okay I think I understand the problems now, but do not know the solution. There appears to be a PHP71 Drupal core problem and also a book_made_simple misuse of the book node edit form api.

FIRST, this code snippet works for PHP56 and not for PHP71

function drupal_array_set_nested_value(array &$array, array $parents, $value, $force = FALSE) {
  $ref = &$array;
  foreach ($parents as $parent) {
    // PHP auto-creates container arrays and NULL entries without error if $ref
    // is NULL, but throws an error if $ref is set, but not an array.
    if ($force && isset($ref) && !is_array($ref)) {
      $ref = array();
    }
    $ref = &$ref[$parent];
  }
  $ref = $value;
}

$array = array('book'=>'');
$parents = array('book','weight');
$value = 'test';
$force = FALSE;
drupal_array_set_nested_value($array, $parents, $value, $force);
print_r('Book as String');
print_r($array);

Explain the above and we will be on our way to understanding the Drupal side of this problem. What I don't understand in my use case / problem is that the $force argument is FALSE which seems to mean that really this should fail for both PHP56 and PHP71. So perhaps it is an accident that it is working for PHP56. Or maybe my PHP ini has a setting that is more permissive for PHP56.

SECOND, $array->book should be an array when this function is called, but is a string instead. As far as I understand it, $array->book is a string instead of an array because I use book_made_simple to change a book vertical tab form item to 'hidden'. Then the form is submitted and rebuilt through the following backtrace...

10: drupal_array_set_nested_value() (Array, 2 elements)
 9: _form_builder_handle_input_element() (Array, 2 elements)
 8: form_builder() (Array, 2 elements)
 7: form_builder() (Array, 2 elements)
 6: form_builder() (Array, 2 elements)
 5: drupal_process_form() (Array, 2 elements)
 4: drupal_build_form() (Array, 2 elements)
 3: drupal_get_form() (Array, 2 elements)
 2: node_page_edit() (Array, 2 elements)
 1: menu_execute_active_handler() (Array, 2 elements)
 0: main() (Array, 2 elements)

At this point since the book node vertical form elements were hidden, then the $form_state['input'] array is never assigned $form_state['input']['book']['weight']. So when drupal_array_set_nested_value() is called with the values demonstrated above... barf!

So in conclusion the Drupal include/common.inc function drupal_array_set_nested_value() performs differently for PHP56 and PHP71 in my configuration and is the reason that my use of book_made_simple when from working to not working.

Changing line 2102 in drupal/includes/form.inc from this

drupal_array_set_nested_value($form_state['input'], $element['#parents'], NULL);

to this

drupal_array_set_nested_value($form_state['input'], $element['#parents'], NULL, TRUE);

fixes the problem and allows my use case to work in PHP56 and PHP71.

However, I don't know if that is the real fix. Drupal core experts?

Thanks. So any input on the best solution? Should this issue be moved back to the Drupal queue?

Seems to me this issue needs to move back to Drupal core / base system since drupal_array_set_nested_value() is a base system function which performs differently between PHP56 and PHP71. That is a core issue. I would have moved the issue back myself, but wasn't sure which Drupal project to pick from the pull down.

if book_made_simple sets $form['book']['#access'] = FALSE will the Drupal form processor then still assign the default value for all the contained fields on update?

Okay, understood. Thanks.

Unfortunately this module does not seem to be well maintained, so I need to decide whether to limp along with a custom patch or find an alternative.

This module has an excellent feature of presenting an add child page button at the bottom of book and child pages so that novice content creators can create books super easily. I wonder if there are other alternatives?

Thanks for the patch offer. However, after the radio silence from book_made_simple maintainers in the queue and email I decided to hack a quick fix. I just liked the access to book reordering from a tab on the book and also expanded links to add children of various contents types from the book. I never understood why Drupal core only allows you to choose one content type for the add child link when many content types might be added as a child.

Note, if the maintainers do not follow up, this module is broken for PHP71.

It is like you say this modules fault and not Drupals. However, I do still find the different performance of drupal_array_set_nested_value() between PHP56 and PHP71 disturbing. Seems like that should be visited so that the performance is the same. Really book_made_simple should have been breaking for PHP56. I wonder if any other code would be impacted when moving to PHP71.

Anyway here is my replacement code for the book_made_simple functions that I needed for any followers. I also used the 'prepopulate' module to help make my code below pretty simple.

function custom_menu() {
	$items = array();
	$items['node/%node/book/parent'] = array(
		'title' => t('Book Home'),
		'page callback' => 'custom_menu_book_parent',
		'page arguments' => array(1),
		'access callback' => 'custom_menu_book_parent_access',
		'access arguments' => array(1),
		'type' => MENU_LOCAL_TASK,
		'weight' => 40,
	);
	$items['node/%node/book/children'] = array(
		'title' => t('Book Pages'),
		'page callback' => 'custom_menu_book_children',
		'page arguments' => array(1),
		'access callback' => 'custom_menu_book_menu_access',
		'access arguments' => array(1),
		'type' => MENU_LOCAL_TASK,
		'weight' => 41,
	);
	$items['node/%node/book/add/page'] = array(
		'title' => t('Add Page'),
		'page callback' => 'custom_menu_book_add_page',
		'page arguments' => array(1),
		'access callback' => 'custom_menu_book_menu_access',
		'access arguments' => array(1),
		'type' => MENU_LOCAL_TASK,
		'weight' => 42,
	);
	$items['node/%node/book/add/poll'] = array(
		'title' => t('Add Poll'),
		'page callback' => 'custom_menu_book_add_poll',
		'page arguments' => array(1),
		'access callback' => 'custom_menu_book_menu_access',
		'access arguments' => array(1),
		'type' => MENU_LOCAL_TASK,
		'weight' => 43,
	);
	$items['node/%node/book/add/h5p'] = array(
		'title' => t('Add H5P'),
		'page callback' => 'custom_menu_book_add_h5p',
		'page arguments' => array(1),
		'access callback' => 'custom_menu_book_menu_access',
		'access arguments' => array(1),
		'type' => MENU_LOCAL_TASK,
		'weight' => 44,
	);
	$items['node/%node/book/add/webform'] = array(
		'title' => t('Add Webform'),
		'page callback' => 'custom_menu_book_add_webform',
		'page arguments' => array(1),
		'access callback' => 'custom_menu_book_menu_access',
		'access arguments' => array(1),
		'type' => MENU_LOCAL_TASK,
		'weight' => 45,
	);
	return $items;
}
function custom_menu_book_parent_access($node) {
	if (!empty($node->book['bid']) && $node->nid!=$node->book['bid']) { return TRUE; }
	return FALSE;
}
function custom_menu_book_parent($node) {
	drupal_goto('node/'.$node->book['bid']);
}
function custom_menu_book_children($node) {
	drupal_goto('admin/content/book/'.$node->book['bid'].'/reorder', array('query' => array("destination" => "node/".$node->nid)));
}
function custom_menu_book_add_page($node) {
	drupal_goto('node/add/page', array('query' => array('edit[book][bid]' => $node->nid)));
}
function custom_menu_book_add_poll($node) {
	drupal_goto('node/add/poll', array('query' => array('edit[book][bid]' => $node->nid)));
}
function custom_menu_book_add_h5p($node) {
	drupal_goto('node/add/h5p-content', array('query' => array('edit[book][bid]' => $node->nid)));
}
function custom_menu_book_add_webform($node) {
	drupal_goto('node/add/webform', array('query' => array('edit[book][bid]' => $node->nid)));
}

Changing to major since book_made_simple misuses the form api and is broken for PHP71.

I am now fully on PHP71 and have abandoned the book_made_simple module. I may not be much further help here. I found it easier to maintain the small code in #26 for my needs than to continue working with book_made_simple.

Best wishes.