When compiling with aspell-0.50.3 (using --with-pspell), everything works fine until the final stages (when sapi/cli/php is created).  At that  point I get multiple errors such as:

Undefined                       first referenced
 symbol                             in file
aspell_speller_store_replacement    ext/pspell/pspell.lo
aspell_speller_add_to_session       ext/pspell/pspell.lo
delete_aspell_speller               ext/pspell/pspell.lo
...
etc.  It appears that the problem is that PHP is including the pspell library but not the newer aspell library, where all those symbols can be found.

The solution that worked for me was to edit the "configure" script, find the section where "-lpspell" is prepended to the $LIBS variables, and add "-laspell" as well.  e.g. on line 62147 for PHP 4.3.1's "configure file", change:

      LIBS="-lpspell $LIBS"
to
      LIBS="-laspell -lpspell $LIBS"