Rotates the src_im image using a given angle in degrees. bgd_color specifies the color of the uncovered zone after the rotation.
The center of rotation is the center of the image, and the rotated image is scaled down so that the whole rotated image fits in the destination image - the edges are not clipped.
If ignore_transparent is set and non-zero, transparent colors are ignored (otherwise kept). This parameter was added in PHP 5.1.
Note: This function is only available if PHP is compiled with the bundled version of the GD library.