Creating a new PHPExcel Object.

$this->PHPExcel = new PHPExcel();

A new sheet can be added to the excel file using:
$this->activeSheet = $this->PHPExcel->createSheet();
and the sheet title can be set or renamed using:
$this->activeSheet->setTitle($title);

Getting the active sheet:
$this->activeSheet = $this->PHPExcel->getActiveSheet();

Setting the active sheet:

$sheetIndex = 2;
$this->PHPExcel->setActiveSheetIndex($sheetIndex)

Setting the width of a specific column.

$this->activeSheet
    ->getColumnDimension($colString)
    ->setWidth($width);

Setting the default column width/row height for an entire sheet.

$this->activeSheet
    ->getDefaultColumnDimension()
    ->setWidth($width);
    
$this->activeSheet
    ->getDefaultRowDimension()
    ->setRowHeight($height);

Setting default styles for the active sheet

$this->activeSheet
    ->getDefaultStyle()
    ->applyFromArray($this->defaultStyle);

To set the value of a cell:

    $this->activeSheet->setCellValue($column.$row, $data);   
    
    $this->activeSheet->setCellValueByColumnAndRow($column, $row, $data);  

    $this->activeSheet->setCellValueExplicit($coord, $value, $dataType);  
    $this->activeSheet->setCellValueExplicitByColumnAndRow($col, $row, $value, $dataType);  

A 2-dimensional array can be written to the current sheet usng fromArray($twoDimArray)

• $twoDimArray - the 2D array to be written
• $useWhenNull - what to use if there is a null value
• $topLeftCorner - where the top left corner should be.

$this->activeSheet->fromArray($sheet);  
$this->activeSheet->fromArray($sheet, "", $colRow);  

Or the array can be written manually by looping through the array and calling setCellValue

foreach($rows as $row => $columns) {
    foreach($columns as $column => $data) {
        $this->activeSheet->setCellValue($column.$row, $data);
    }
}