If update.php cannot reach the database server, it should return 1 to
the calling shell, not 0.
0 indicates success, 1 indicates failure.
Else scripts have no way to detect failure occurred.
"Set $wgShowExceptionDetails = true; and $wgShowDBErrorBacktrace = true;
at the bottom of LocalSettings.php to show detailed debugging
Is just general debugging advice.
It needs to be preceded by
ERROR: DATABASE SERVER NOT REACHED, NO UPDATE PREFORMED.