In change 686626, LogEventsList.php was written as follows (reduced example):
public static function showLogExtract( &$out, $types = [], $page = '', $user = '', $param = [] ) { $pager = new LogPager(); $numRows = $pager->getNumRows(); if ( $page instanceof PageReference ) { $pageName = 'db key here'; } elseif ( $page != '' ) { $pageName = $page; } if ( $numRows > $pager->mLimit ) { $urlParam = []; $urlParam['page'] = $pageName; } }
This caused Undefined variable: $pageName, as reported and fixed in T282834.
This task is to understand why our automation tool )Phan) didn't catch this case of a conditionally-defined variable, used under no condition (or a different condition).