imagecopyresampled() copies a rectangular portion of one image to another image, smoothly interpolating pixel values so that, in particular, reducing the size of an image still retains a great deal of clarity. Dst_im is the destination image, src_im is the source image identifier. If the source and destination coordinates and width and heights differ, appropriate stretching or shrinking of the image fragment will be performed. The coordinates refer to the upper left corner. This function can be used to copy regions within the same image (if dst_im is the same as src_im) but if the regions overlap the results will be unpredictable.
See also imagecopyresized().
Note: This function was added in PHP 4.0.6 and requires GD 2.0.1 or later