flush(); is needed after
print "<br><br><a href=\"upgrade.php?upgrade=311&step=2\">Move DATA directory files (you only do this only once successfully) --></a> or quit here.<br />
Moving data files can take some time depending on your installation; 10,000 files could take 5 minutes or more. Please be patient.";
print "</td></tr></table></td></tr></table>";