hook_menu() has been removed from Drupal 8.
Documentation
Files Affected
drupal_set_title() has been removed.
Documentation
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drupal_get_form() has moved into the FormBuilder service.
Documentation
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l() has been removed.
Documentation
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drupal_strtolower() has been moved into the Unicode utility class.
Documentation
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variable_del() has been removed.
Documentation
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variable_get() has been removed.
Documentation
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variable_set() has been removed.
Documentation
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Many common functions, shared variables, and constants have been renamed.
Documentation
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
Automated web tests must be in a PSR-4 namespace, and unit tests must be converted to PHPUnit.
Documentation