imagesetstyle() sets the style to be used by all line drawing functions (such as imageline() and imagepolygon()) when drawing with the special color IMG_COLOR_STYLED or lines of images with color IMG_COLOR_STYLEDBRUSHED.
image
An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
style
An array of pixel colors. You can use the IMG_COLOR_TRANSPARENT constant to add a transparent pixel.
Following example script draws a dashed line from upper left to lower right corner of the canvas: