--- php-5.2.0/configure.ac.includedir
+++ php-5.2.0/configure.ac
@@ -1101,7 +1101,7 @@
 EXPANDED_DATADIR=$datadir
 EXPANDED_PHP_CONFIG_FILE_PATH=`eval echo "$PHP_CONFIG_FILE_PATH"`
 EXPANDED_PHP_CONFIG_FILE_SCAN_DIR=`eval echo "$PHP_CONFIG_FILE_SCAN_DIR"`
-INCLUDE_PATH=.:$EXPANDED_PEAR_INSTALLDIR
+INCLUDE_PATH=.:$EXPANDED_PEAR_INSTALLDIR:${EXPANDED_DATADIR}/php
 
 exec_prefix=$old_exec_prefix
 libdir=$old_libdir