I am trying to read a cell with possible trailing zeros as a string instead of numeric (which strips off leading zeros). The cell is read by integer column/row as below instead
$keyCell = $sheet->getCellByColumnAndRow(1,5)->getValue();
Will read the cell data in the format that it's actually stored by Excel, you can't arbitrarily change that or tell PHPExcel to read it as a different datatype.
However, if the cell has formatting applied, then you can use
$keyCell = $sheet->getCellByColumnAndRow(1,5)->getFormattedValue();
instead, and this will return the data as a string, with whatever format mask was defined in the Excel spreadsheet