This function is currently not documented; only the argument list is available.
This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change without notice in a future release of PHP. Use this function at your own risk.
Swirls the pixels about the center of the image, where degrees indicates the sweep of the arc through which each pixel is moved. You get a more dramatic effect as the degrees move from 1 to 360.