update_requirements($phase)
Implements hook_requirements().
Return value
An array describing the status of the site regarding available updates. If there is no update data, only one record will be returned, indicating that the status of core can't be determined. If data is available, there will be two records: one for core, and another for all of contrib (assuming there are any contributed modules or themes enabled on the site). In addition to the fields expected by hook_requirements ('value',