This class can be used to plot a graphic of a function given its expression.
*** This class requires EvalMath by Miles Kaufmann http://www.phpclasses.org/evalmath for better expression evaluation before plotting. ***
It can evaluate the given function for a given interval of x and y variable values and draw lines between the calculated points.
The class also draws a grid of scale values as well the X and Y axis.
More than one graphic can be rendered in the same image. The resulting image is outputted in the PNG format.