Here is example for trendlines. Trendline can apply to Scatter Charts, Bar Charts, Column Charts, and Line Charts in which both X and Y are number

<?php
ColumnChart::create(array(
    "dataSource"=>array(
        array("cat","amount"),
        array(1,3),
        array(2,8),
        array(3,10),
        array(4,15),
        array(5,18),
    ),
    "columns"=>array("cat","amount"),
    "options"=>array(
        "trendlines"=> array(
            0=>array()
        )
    )
));
?>