Draws a string vertically at the given
coordinates.
imageAn image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
fontCan be 1, 2, 3, 4, 5 for built-in fonts (where higher numbers corresponding to larger fonts) or any of your own font identifiers registered with imageloadfont().
xx-coordinate of the upper left corner
yy-coordinate of the upper left corner
sringThe string to be written
colorA color identifier created with imagecolorallocate()