In custom searches, column headings are being ignored
For custom searches - ones that come installed with core CiviCRM as well as user-defined ones - the column headings defined in the custom search code are being ignored. This issue affects CiviCRM 5.0.0.
Each custom search is implemented by a class that extends CRM_Contact_Form_Search_Custom_Base and implements CRM_Contact_Form_Search_Interface. The columns displayed for search results are defined by either $this->_columns or the columns() method. The keys of this array should set the column headings, but they are being ignored.
When the search results are displayed, the specified headings are not used. Instead, some columns are given default headings and others are missing headings. This means that the results can't be sorted on those columns.
To reproduce this bug, click Search ⇒ Custom Searches, then pick a contact search, e.g. "Basic Search", "Include / Exclude Search" or "Postal Mailing", enter search criteria that will select some contacts, and then click Search. In the results you'll see that the column headings do not match the ones defined in the custom search class, and some columns (e.g. street address, phone number, contact type, etc) have no headings at all.