hook_entity_info() has been removed.
Documentation
Files Affected
hook_menu() has been removed from Drupal 8.
Documentation
Files Affected
drupal_add_js() has been removed.
Documentation
Files Affected
confirm_form() is now \Drupal\Core\Form\ConfirmFormBase
Documentation
Files Affected
Most CTools APIs have moved into core.
Documentation
Files Affected
The CTools object caching system has moved into core.
Documentation
Files Affected
The CTools object caching system has moved into core.
Documentation
Files Affected
drupal_goto() has been removed.
Documentation
Files Affected
drupal_render() has been removed.
Files Affected
element_children() is now a method of the Element class.
Documentation
Files Affected
entity_create() is now a method of EntityInterface.
Documentation
Files Affected
entity_load() has been removed.
Documentation
Files Affected
entity_save() has been removed.
Documentation
Files Affected
entity_delete() has been removed.
Documentation
Files Affected
node_load_multiple() has been removed.
Documentation
Files Affected
field_update_field() is now FieldStorageConfig::save().
Documentation
Files Affected
field_update_instance() is now FieldConfig::save().
Documentation
Files Affected
form_set_error() is now a method of FormStateInterface.
Documentation
Files Affected
format_interval() was moved into the date.formatter service.
Documentation
Files Affected
format_plural() was moved into the translation service.
Documentation
Files Affected
drupal_html_id() has been moved into the HTML component.
Documentation
Files Affected
l() has been removed.
Documentation
Files Affected
menu_parent_options() has been replaced by menu.link_tree service.
Documentation
Files Affected
get_t() has been removed.
Documentation
Files Affected
theme() has been renamed to _theme(), and should never be called directly.
Documentation
Files Affected
variable_del() has been removed.
Documentation
Files Affected
variable_get() has been removed.
Documentation
Files Affected
variable_set() has been removed.
Documentation
Files Affected
watchdog() has been removed.
Documentation
Files Affected
Many common functions, shared variables, and constants have been renamed.
Documentation
The signature of hook_form_alter() has changed in Drupal 8.
Documentation
Files Affected
Static permissions are now defined in MODULE.permissions.yml.
Documentation
Files Affected

This issue can be fixed automatically.

Default configuration is deleted automatically.
Files Affected
Module info files' core key must have a value of 8.x.
Documentation
Files Affected
Info files must contain a type key.
Documentation
Files Affected
Many common dependencies have moved into core.
Documentation
Files Affected
Modules no longer declare classes in their info file.
Documentation
Files Affected
Module info files' configure key must be a route name, not a path.
Documentation
Files Affected
Classes must be PSR-4 compliant.
Documentation
Automated web tests must be in a PSR-4 namespace, and unit tests must be converted to PHPUnit.
Documentation