Debian's apache2-dev and libapr0-dev packages put headers in different places; /usr/include/apache2 and /usr/include/apr-0,  respectively.  Unfortunately, apxs2 doesn't output the location of apr headers, which is required in order to compile.

So, compilation ends up failing w/:

/bin/sh /home/dilinger/php-4.3.2/libtool --silent --preserve-dup-deps --mode=compile /home/dilinger/php-4.3.2/meta_ccld  -Isapi/apache2handler/ -I/home/dilinger/php-4.3.2/sapi/apache2handler/ -DPHP_ATOM_INC -I/home/dilinger/php-4.3.2/include -I/home/dilinger/php-4.3.2/main -I/home/dilinger/php-4.3.2 -I/usr/include/apache2 -I/home/dilinger/php-4.3.2/Zend -I/usr/include/libxml2 -I/usr/include/mysql
-I/home/dilinger/php-4.3.2/ext/xml/expat  -D_REENTRANT -I/home/dilinger/php-4.3.2/TSRM  -g -O2 -pthread -DZTS  -prefer-pic -c /home/dilinger/php-4.3.2/sapi/apache2handler/sapi_apache2.c -o sapi/apache2handler/sapi_apache2.lo
/home/dilinger/php-4.3.2/sapi/apache2handler/sapi_apache2.c:38:25: apr_strings.h: No such file or directory


Here's the output of apr-config --includes:

 -I/usr/include/apr-0

This is something that the apache folks know about, but isn't likely to change anytime soon, due to the rather lame apxs interface they've standardized on.  So, it would be nice if php worked around this.

The simplest way to fix this is to add
  CPPFLAGS="$CPPFLAGS `apr-config --includes`"
to sapi/apache2handler/config.m4.