./configure cannot locate header file when the directory is specified with CPPFLAGS

I'm trying to build php gettext module on Mac OS X Mavericks.

Installed gettext with brew install gettext, and checked header files are available at /usr/local/opt/gettext.

$ ls /usr/local/opt/gettext/include/
autosprintf.h   gettext-po.h    libintl.h

With a help in the post of How to override environment variables when running configure?, I executed ./configure LDFLAGS='-L/usr/local/opt/gettext/lib/' CPPFLAGS='-I/usr/local/opt/gettext/include/' to get this error message.

checking if debug is enabled... no
checking if zts is enabled... no
checking for re2c... re2c
checking for re2c version... 0.13.6 (ok)
checking for gawk... gawk
checking for GNU gettext support... yes, shared
configure: error: Cannot locate header file libintl.h <--

What's wrong with this? Why configure cannot find the header file when I specified the directory?

Solution

Looking into the ./configure script, I noticed the script doesn't look into the environmental variable that I give. I just modified the script (Line 4067) to get it work.

if test "$PHP_GETTEXT" != "no"; then
  for i in $PHP_GETTEXT /usr/local /usr /usr/local/opt/gettext; do
    test -r $i/include/libintl.h && GETTEXT_DIR=$i && break
  done