How to convert to 8-bit 256 palleted png using php imagick

If you want to convert and save any image using pure php imagick, to palleted, 8-bit png:

$thumb->setImageType (4); //sets to 256 colors
$thumb->setImageFormat('png');
$thumb->setImageDepth('8'); // :)
$thumb->setImageCompressionQuality(90); //u can try also 95
$thumb->writeImage('temp.png');