SetImageBorderType — Draw a border around the image
$plot->SetImageBorderType($sibt)
SetImageBorderType controls the drawing of a border
around the entire image. By default, no border is drawn.
$sibtA string indicating the desired border type: 'raised' or 'plain'. A plain border is 1 pixel wide. A raised border is 2 pixels wide, with the bottom and left side drawn in a darker color.
The color of the image border is set with SetImageBorderColor. By default, no image border is drawn.
It can be useful to have a border drawn around images when embedded in an HTML page. An alternative to this function is to use the BORDER attribute in the IMG tag when embedding the image. With that attribute, you can also control the border width.