slight changes to config of pdf module

ext/pdf/config.h.stub

@@ -1,2 +1,3 @@
 /* Define if you have the pdflib library */
 #define HAVE_PDFLIB 0
+

ext/pdf/config.m4

@@ -13,7 +13,7 @@ echo $withval
     yes)
       AC_MSG_RESULT(yes)
       PHP_EXTENSION(pdf)
-      AC_CHECK_LIB(pdf, PDF_close, [AC_DEFINE(HAVE_PDFLIB) PDFLIB_LIBS="-lpdf"],
+      AC_CHECK_LIB(pdf, PDF_close, [AC_DEFINE(HAVE_PDFLIB) PDFLIB_LIBS="-lpdf -lz"],
         [AC_MSG_ERROR(pdflib extension requires pdflib 2.0.)])
       EXTRA_LIBS="$EXTRA_LIBS $PDFLIB_LIBS"
       ;;
@@ -24,7 +24,7 @@ echo $withval
         PHP_EXTENSION(pdf)
         old_LIBS=$LIBS
 
-        if test -z $ZLIB_LIBS; then
+        if test $HAVE_ZLIB; then
           old_withval=$withval
           AC_MSG_CHECKING([for zlib (needed by pdflib 2.0)])
           AC_ARG_WITH(zlib-dir,
@@ -39,12 +39,12 @@ echo $withval
             AC_MSG_RESULT(no)
             AC_MSG_WARN(If configure fails try --with-zlib=<DIR>)
           ])
+          withval=$old_withval
         else
           echo "checking for libz needed by pdflib 2.0... already zlib support"
           PDFLIB_LIBS="$ZLIB_LIBS"
-          LIBS="$LIBS $ZLIB_LIBS"
+          LIBS="$LIBS -lz"
         fi
-        withval=$old_withval
 
         LIBS="$LIBS -L$withval/lib"
         AC_CHECK_LIB(pdf, PDF_close, [AC_DEFINE(HAVE_PDFLIB) PDFLIB_LIBS="-L$withval/lib -lpdf"],