diff -u b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php
--- b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php
@@ -296,7 +296,9 @@
       // Let the widget turn the submitted values into actual field values.
       // Make sure the '_weight' entries are persisted in the process.
       $weights = array();
-      if (isset($values[0]['_weight'])) {
+      // Check that $values[0] is an array, because if it's a string, then in
+      // PHP 5.3, ['_weight'] returns the first character.
+      if (isset($values[0]) && is_array($values[0]) && isset($values[0]['_weight'])) {
         foreach ($values as $delta => $value) {
           $weights[$delta] = $value['_weight'];
         }
@@ -416,7 +418,7 @@
     $cardinality = $this->fieldDefinition->getFieldCardinality();
     $is_multiple = ($cardinality == FIELD_CARDINALITY_UNLIMITED) || ($cardinality > 1);
     if ($is_multiple && isset($items[0]->_weight)) {
-      $itemValues = $items->getValue();
+      $itemValues = $items->getValue(TRUE);
       usort($itemValues, function ($a, $b) {
         $a_weight = (is_array($a) ? $a['_weight'] : 0);
         $b_weight = (is_array($b) ? $b['_weight'] : 0);
diff -u b/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatterBase.php b/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatterBase.php
--- b/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatterBase.php
+++ b/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatterBase.php
@@ -43,7 +43,7 @@
             'alt' => '',
             'title' => '',
             'entity' => $file,
-            'fid' => $file->id(),
+            'target_id' => $file->id(),
           )));
         }
       }
only in patch2:
unchanged:
--- a/core/modules/image/lib/Drupal/image/Tests/ImageFieldDefaultImagesTest.php
+++ b/core/modules/image/lib/Drupal/image/Tests/ImageFieldDefaultImagesTest.php
@@ -121,7 +121,7 @@ function testDefaultImages() {
     $article = $this->drupalCreateNode(array('type' => 'article'));
     $article_built = node_view($article);
     $this->assertEqual(
-      $article_built[$field_name]['#items'][0]['fid'],
+      $article_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance']->id(),
       format_string(
         'A new article node without an image has the expected default image file ID of @fid.',
@@ -133,7 +133,7 @@ function testDefaultImages() {
     $page = $this->drupalCreateNode(array('type' => 'page'));
     $page_built = node_view($page);
     $this->assertEqual(
-      $page_built[$field_name]['#items'][0]['fid'],
+      $page_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance2']->id(),
       format_string(
         'A new page node without an image has the expected default image file ID of @fid.',
@@ -160,7 +160,7 @@ function testDefaultImages() {
     $article_built = node_view($article = node_load($article->nid, TRUE));
     $page_built = node_view($page = node_load($page->nid, TRUE));
     $this->assertEqual(
-      $article_built[$field_name]['#items'][0]['fid'],
+      $article_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance']->id(),
       format_string(
         'An existing article node without an image has the expected default image file ID of @fid.',
@@ -168,7 +168,7 @@ function testDefaultImages() {
       )
     );
     $this->assertEqual(
-      $page_built[$field_name]['#items'][0]['fid'],
+      $page_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance2']->id(),
       format_string(
         'An existing page node without an image has the expected default image file ID of @fid.',
@@ -198,7 +198,7 @@ function testDefaultImages() {
 
     // Confirm the article uses the new default.
     $this->assertEqual(
-      $article_built[$field_name]['#items'][0]['fid'],
+      $article_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance_new']->id(),
       format_string(
         'An existing article node without an image has the expected default image file ID of @fid.',
@@ -207,7 +207,7 @@ function testDefaultImages() {
     );
     // Confirm the page remains unchanged.
     $this->assertEqual(
-      $page_built[$field_name]['#items'][0]['fid'],
+      $page_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance2']->id(),
       format_string(
         'An existing page node without an image has the expected default image file ID of @fid.',
@@ -232,7 +232,7 @@ function testDefaultImages() {
     $page_built = node_view($page = node_load($page->nid, TRUE));
     // Confirm the article uses the new field (not instance) default.
     $this->assertEqual(
-      $article_built[$field_name]['#items'][0]['fid'],
+      $article_built[$field_name]['#items'][0]['target_id'],
       $default_images['field_new']->id(),
       format_string(
         'An existing article node without an image has the expected default image file ID of @fid.',
@@ -241,7 +241,7 @@ function testDefaultImages() {
     );
     // Confirm the page remains unchanged.
     $this->assertEqual(
-      $page_built[$field_name]['#items'][0]['fid'],
+      $page_built[$field_name]['#items'][0]['target_id'],
       $default_images['instance2']->id(),
       format_string(
         'An existing page node without an image has the expected default image file ID of @fid.',