Example:

//Instantiating a Workbook object
$workbook = new cells\Workbook();
//Obtaining the reference of the first worksheet
$worksheet = $workbook->getWorksheets()->get(0);
//Add new Style to Workbook
$style = $workbook->createStyle();
//Setting the background color to Blue
$style->setForegroundColor(cells\Color::getBlue());
//setting Background Pattern
$style->setPattern(cells\BackgroundType::SOLID);
//New Style Flag
$styleFlag = new cells\StyleFlag();
//Set All Styles
$styleFlag->setAll(true);

//Change the default width of first ten columns
for ($i = 0; $i < 10; $i++)
{
    $worksheet->getCells()->getColumns()->get($i)->setWidth(20);
}

//Get the Column with non default formatting
$columns = $worksheet->getCells()->getColumns();
for ($o = $columns->iterator(); java_values($o->hasNext());)
{
    $column = $o->next();
    echo "Apply style to column-".$column->getIndex()."\n";
    //Apply Style to first ten Columns
    $column->applyStyle($style, $styleFlag);
}