PHP Header issue with ob_start() and ob_end_flush()

Question

I get header problem while I use ob_start() in the beginning of a page and ob_end_flush() at the end. Because I use header function after some quer

Answer 1

I'm a bit baffled the warning message doesn't include the location of the code that caused the first content to be sent to the client. The function headers_sent() can return that location, too. So, for debugging purposes, please try

if($delHourExist)
{
  if ( headers_sent($path, $lineno) ) {
    echo '
Debug: output started at ', $path, ':', $lineno, "
\n";
  }
  header("location: edit_delivery_hours.php");
}