The gd package has changed from GIF to PNG support as of version 1.7.3

This breaks the php-4.0b2/ext/gd/gd.c

From the gd 1.7.3 source:
/*---------------------------------------------------------------------------

    gd_png.c                 Copyright 1999 Greg Roelofs and Thomas Boutell

    The routines in this file, gdImagePng*() and gdImageCreateFromPng*(),
    are drop-in replacements for gdImageGif*() and gdImageCreateFromGif*(),
    except that these functions are noisier in the case of errors (comment
    out all fprintf() statements to disable that).

    Only GIF-like PNG features are currently supported; that is, images must
    either be indexed-color to begin with or they will be converted to it,
    and they can have, at most, a single, fully transparent palette entry or
    color.  (Alpha channels are ignored.)  Since gd images are artificially
    generated, gamma is also ignored, and there is currently no support for
    embedded text annotations (a la GIF comments) in gd.

    Last updated:  19 July 1999

  ---------------------------------------------------------------------------*/

Finally, also in php's gd.c the function gdImageColorResolve is no provided in gd-1.7.3 library... get's a defined twice error during Apache link.