openPlaG is a PHP based function graph plotter for use on websites. It was first released in April 2006. In June 2007 its source code was published under the GNU GPL license. PlaG is an abbreviation for Plot a Graph. About 180 functions are predefined. These belong to the categories basic functions, trigonometric and hyperbolic functions, non-differentiable functions, probability functions, special functions, programmable functions, iterations and fractals, differential and integral equations.