$min_x = $x_axis[0];
$pts = array();
$pts[] = array('x' => 0, 'y' => $origin_y);
/*
for ($i = 0; $i < count($data[$j]); $i++)
{
$pts[] = array('x' => ($i * $gap), 'y' => ($height - $data[$j][$i]/$max*$height) + $origin_y);
}
*/
//print_r($data[$headings[$j]]);
foreach ($data[$headings[$j]] as $k => $v) {
$pts[] = array('x' => ($k - $x_axis[0]) * $gap, 'y' => $height - $v / $max * $height + $origin_y);
}
$pts[] = array('x' => (count($x_axis) - 1) * $gap, 'y' => $origin_y + $height);
$pts[] = array('x' => 0, 'y' => $origin_y + $height);
$pts[] = array('x' => 0, 'y' => $origin_y);
$port->DrawPolygon($pts, array(228, 228, 228));
// function DrawText ($pt, $text, $fontsize = 0.1, $align = 'left')
$fontsize = 20;
$port->DrawText(array('x' => count($x_axis) * $gap + $fontsize / 2, 'y' => $origin_y + $fontsize), $headings[$j], $fontsize);
}
// time scale
$ticks = array(1864, 1900, 1950, 2000, 1923, 2015);
foreach ($ticks as $tick) {
$port->DrawLine(array('x' => ($tick - $x_axis[0]) * $gap, 'y' => 0), array('x' => ($tick - $x_axis[0]) * $gap, 'y' => (count($headings) - 1) * $height));
$fontsize = 20;
$port->DrawText(array('x' => ($tick - $x_axis[0]) * $gap, 'y' => (count($headings) - 1) * $height + $fontsize), $tick, $fontsize);
}
echo $port->GetOutput();