I did not find an answer in documentation and did not find simmilar tread on forum.
When hovering the cell of column 1 the tooltip should be shown from column 32 which is hidden:
I found how to show the tooltip given by text in code, but I don't know how to refer to another column.
<?php
$col1 = new EJ\Grid\Column(); $col1->field("id")->headerText("ID")->textAlign("center")->visible(false)->width(20);
$col2 = new EJ\Grid\Column(); $col2->field("dealer")->headerText("Dealer")->textAlign("left")->width(70)->tooltip("Commentary");
$col3 = new EJ\Grid\Column(); $col3->field("shift")->headerText("Shift")->textAlign("center")->width(45);
$col4 = new EJ\Grid\Column(); $col4->field('d1')->headerText('1 <small>Sun</small>')->textAlign('center')->width(30);
$col5 = new EJ\Grid\Column(); $col5->field('d2')->headerText('2 Mon')->textAlign('center')->width(30);
$col6 = new EJ\Grid\Column(); $col6->field('d3')->headerText('3 Tue')->textAlign('center')->width(30);
$col7 = new EJ\Grid\Column(); $col7->field('d4')->headerText('4 Wed')->textAlign('center')->width(30);
$col8 = new EJ\Grid\Column(); $col8->field('d5')->headerText('5 Thu')->textAlign('center')->width(30);
$col9 = new EJ\Grid\Column(); $col9->field('d6')->headerText('6 Fri')->textAlign('center')->width(30);
$col10 = new EJ\Grid\Column(); $col10->field('d7')->headerText('7 Sat')->textAlign('center')->width(30);
$col11 = new EJ\Grid\Column(); $col11->field('d8')->headerText('8 Sun')->textAlign('center')->width(30);
$col12 = new EJ\Grid\Column(); $col12->field('d9')->headerText('9 Mon')->textAlign('center')->width(30);
$col13 = new EJ\Grid\Column(); $col13->field('d10')->headerText('10 Tue')->textAlign('center')->allowResizing(true)->width(30);
$col14 = new EJ\Grid\Column(); $col14->field('d11')->headerText('11 Wed')->textAlign('center')->width(30);
$col15 = new EJ\Grid\Column(); $col15->field('d12')->headerText('12 Thu')->textAlign('center')->width(30);
$col16 = new EJ\Grid\Column(); $col16->field('d13')->headerText('13 Fri')->textAlign('center')->width(30);
$col17 = new EJ\Grid\Column(); $col17->field('d14')->headerText('14 Sat')->textAlign('center')->width(30);
$col18 = new EJ\Grid\Column(); $col18->field('d15')->headerText('15 Sun')->textAlign('center')->width(30);
$col19 = new EJ\Grid\Column(); $col19->field('d16')->headerText('16 Mon')->textAlign('center')->width(30);
$col20 = new EJ\Grid\Column(); $col20->field('d17')->headerText('17 Tue')->textAlign('center')->width(30);
$col21 = new EJ\Grid\Column(); $col21->field('d18')->headerText('18 Wed')->textAlign('center')->width(30);
$col22 = new EJ\Grid\Column(); $col22->field('d19')->headerText('19 Thu')->textAlign('center')->width(30);
$col23 = new EJ\Grid\Column(); $col23->field('d20')->headerText('20 Fri')->textAlign('center')->width(30);
$col24 = new EJ\Grid\Column(); $col24->field('d21')->headerText('21 Sat')->textAlign('center')->width(30);
$col25 = new EJ\Grid\Column(); $col25->field('d22')->headerText('22 Sun')->textAlign('center')->width(30);
$col26 = new EJ\Grid\Column(); $col26->field('d23')->headerText('23 Mon')->textAlign('center')->width(30);
$col27 = new EJ\Grid\Column(); $col27->field('d24')->headerText('24 Tue')->textAlign('center')->width(30);
$col28 = new EJ\Grid\Column(); $col28->field('d25')->headerText('25 Wed')->textAlign('center')->width(30);
$col29 = new EJ\Grid\Column(); $col29->field('d26')->headerText('26 Thu')->textAlign('center')->width(30);
$col30 = new EJ\Grid\Column(); $col30->field('d27')->headerText('27 Fri')->textAlign('center')->width(30);
$col31 = new EJ\Grid\Column(); $col31->field('d28')->headerText('28 Sat')->textAlign('center')->width(30);
$col32 = new EJ\Grid\Column(); $col32->field('d29')->headerText('29 Sun')->textAlign('center')->width(30);
$col33 = new EJ\Grid\Column(); $col33->field('d30')->headerText('30 Mon')->textAlign('center')->width(30);
$col34 = new EJ\Grid\Column(); $col34->field('d31')->headerText('31 Tue')->textAlign('center')->width(30);
$gridColumns = array($col1, $col2, $col3, $col4, $col5, $col6, $col7, $col8, $col9, $col10, $col11, $col12, $col13, $col14, $col15, $col16, $col17, $col18, $col19, $col20, $col21, $col22,
$col23, $col24, $col25, $col26, $col27, $col28, $col29, $col30, $col31, $col32, $col33, $col34);
$dataManager = new EJ\DataManager();
$dataManager->url(get_theme_file_uri( 'staffgridjson.php' ))->adaptor('UrlAdaptor');
$grid = new EJ\Grid("Grid");
echo $grid -> dataSource( $dataManager)->columns($gridColumns)->allowPaging(true)->render();
?>
As on screenshot above, I want to show Sun, Tue, etc. below the dates. Unfortunatelly, the heigth of row is not big enough and since I do not see how I can resize it, it can be solved with stackedHeaderRows which I can find in functions, but can not find any documentation on how to use this fucntion in PHP. In Javascript everything looks clear. Please, see my code above as well.