Beginning with PHP 4.3, bits and channels are present for other image types, too.
Returns an array with 4 elements. Index 0 contains the width of the image in pixels. Index 1 contains the height. Index 2 a flag indicating the type of the image. 1 = GIF, 2 = JPG, 3 = PNG, 4 = SWF. Index 3 is a text string with the correct "height=xxx width=xxx" string that can be used directly in an IMG tag.