I don't have much experience working with php but from a logic standpoint this is what I would do.
Below is some pseudocode illustrating this technique:
for (int i = 0; i < MySQLResults.count; i++){
$objPHPExcel->getActiveSheet()->setCellValue('A' . (string)(i + 1), MySQLResults[i].name);
// Add 1 to i because Excel Rows start at 1, not 0, so row will always be one off
$objPHPExcel->getActiveSheet()->setCellValue('B' . (string)(i + 1), MySQLResults[i].number);
$objPHPExcel->getActiveSheet()->setCellValue('C' . (string)(i + 1), MySQLResults[i].email);
}