Adapted for 5.6 from 

From 397bedcc7c3545510a22b7db8dc6444e0a05b085 Mon Sep 17 00:00:00 2001
From: Remi Collet <remi@php.net>
Date: Wed, 16 Nov 2016 10:45:59 +0100
Subject: [PATCH] Fixed bug #73512 Fails to find firebird headers

- use fb_config output instead of relying on hardoded path

diff -up ./ext/interbase/config.m4.fb_config ./ext/interbase/config.m4
--- ./ext/interbase/config.m4.fb_config	2017-03-17 08:58:57.061708947 +0100
+++ ./ext/interbase/config.m4	2017-03-17 09:04:53.389584385 +0100
@@ -3,39 +3,54 @@ PHP_ARG_WITH(interbase,for InterBase sup
                           install directory [/usr/interbase]])
 
 if test "$PHP_INTERBASE" != "no"; then
-  if test "$PHP_INTERBASE" = "yes"; then
-    IBASE_INCDIR=/usr/interbase/include
-    IBASE_LIBDIR=/usr/interbase/lib
+
+  AC_PATH_PROG(FB_CONFIG, fb_config, no)
+
+  if test -x "$FB_CONFIG" && test "$PHP_INTERBASE" = "yes"; then
+    AC_MSG_CHECKING(for libfbconfig)
+    FB_CFLAGS=`$FB_CONFIG --cflags`
+    FB_LIBDIR=`$FB_CONFIG --libs`
+    FB_VERSION=`$FB_CONFIG --version`
+    AC_MSG_RESULT(version $FB_VERSION)
+    PHP_EVAL_LIBLINE($FB_LIBDIR, INTERBASE_SHARED_LIBADD)
+    PHP_EVAL_INCLINE($FB_CFLAGS)
+
   else
-    IBASE_INCDIR=$PHP_INTERBASE/include
-    IBASE_LIBDIR=$PHP_INTERBASE/$PHP_LIBDIR
-  fi
+    if test "$PHP_INTERBASE" = "yes"; then
+      IBASE_INCDIR=/usr/interbase/include
+      IBASE_LIBDIR=/usr/interbase/lib
+    else
+      IBASE_INCDIR=$PHP_INTERBASE/include
+      IBASE_LIBDIR=$PHP_INTERBASE/$PHP_LIBDIR
+    fi
 
-  PHP_CHECK_LIBRARY(fbclient, isc_detach_database,
-  [
-    IBASE_LIBNAME=fbclient
-  ], [
-    PHP_CHECK_LIBRARY(gds, isc_detach_database,
+    PHP_CHECK_LIBRARY(fbclient, isc_detach_database,
     [
-      IBASE_LIBNAME=gds
+      IBASE_LIBNAME=fbclient
     ], [
-      PHP_CHECK_LIBRARY(ib_util, isc_detach_database,
+      PHP_CHECK_LIBRARY(gds, isc_detach_database,
       [
-        IBASE_LIBNAME=ib_util
+        IBASE_LIBNAME=gds
       ], [
-        AC_MSG_ERROR([libgds, libib_util or libfbclient not found! Check config.log for more information.])
+        PHP_CHECK_LIBRARY(ib_util, isc_detach_database,
+        [
+          IBASE_LIBNAME=ib_util
+        ], [
+          AC_MSG_ERROR([libgds, libib_util or libfbclient not found! Check config.log for more information.])
+        ], [
+          -L$IBASE_LIBDIR
+        ])
       ], [
         -L$IBASE_LIBDIR
       ])
     ], [
       -L$IBASE_LIBDIR
     ])
-  ], [
-    -L$IBASE_LIBDIR
-  ])
   
-  PHP_ADD_LIBRARY_WITH_PATH($IBASE_LIBNAME, $IBASE_LIBDIR, INTERBASE_SHARED_LIBADD)
-  PHP_ADD_INCLUDE($IBASE_INCDIR)
+    PHP_ADD_LIBRARY_WITH_PATH($IBASE_LIBNAME, $IBASE_LIBDIR, INTERBASE_SHARED_LIBADD)
+    PHP_ADD_INCLUDE($IBASE_INCDIR)
+  fi
+
   AC_DEFINE(HAVE_IBASE,1,[ ])
   PHP_NEW_EXTENSION(interbase, interbase.c ibase_query.c ibase_service.c ibase_events.c ibase_blobs.c, $ext_shared)
   PHP_SUBST(INTERBASE_SHARED_LIBADD)
diff -up ./ext/pdo_firebird/config.m4.fb_config ./ext/pdo_firebird/config.m4
--- ./ext/pdo_firebird/config.m4.fb_config	2017-01-19 01:17:47.000000000 +0100
+++ ./ext/pdo_firebird/config.m4	2017-03-17 08:58:57.061708947 +0100
@@ -8,43 +8,56 @@ if test "$PHP_PDO_FIREBIRD" != "no"; the
     AC_MSG_ERROR([PDO is not enabled! Add --enable-pdo to your configure line.])
   fi
 
-  if test "$PHP_PDO_FIREBIRD" = "yes"; then
-    FIREBIRD_INCDIR=
-    FIREBIRD_LIBDIR=
-    FIREBIRD_LIBDIR_FLAG=
+  AC_PATH_PROG(FB_CONFIG, fb_config, no)
+
+  if test -x "$FB_CONFIG" && test "$PHP_PDO_FIREBIRD" = "yes"; then
+    AC_MSG_CHECKING(for libfbconfig)
+    FB_CFLAGS=`$FB_CONFIG --cflags`
+    FB_LIBDIR=`$FB_CONFIG --libs`
+    FB_VERSION=`$FB_CONFIG --version`
+    AC_MSG_RESULT(version $FB_VERSION)
+    PHP_EVAL_LIBLINE($FB_LIBDIR, PDO_FIREBIRD_SHARED_LIBADD)
+    PHP_EVAL_INCLINE($FB_CFLAGS)
+
   else
-    FIREBIRD_INCDIR=$PHP_PDO_FIREBIRD/include
-    FIREBIRD_LIBDIR=$PHP_PDO_FIREBIRD/$PHP_LIBDIR
-    FIREBIRD_LIBDIR_FLAG=-L$FIREBIRD_LIBDIR
-  fi
+    if test "$PHP_PDO_FIREBIRD" = "yes"; then
+      FIREBIRD_INCDIR=
+      FIREBIRD_LIBDIR=
+      FIREBIRD_LIBDIR_FLAG=
+    else
+      FIREBIRD_INCDIR=$PHP_PDO_FIREBIRD/include
+      FIREBIRD_LIBDIR=$PHP_PDO_FIREBIRD/$PHP_LIBDIR
+      FIREBIRD_LIBDIR_FLAG=-L$FIREBIRD_LIBDIR
+    fi
 
-  PHP_CHECK_LIBRARY(fbclient, isc_detach_database,
-  [
-    FIREBIRD_LIBNAME=fbclient
-  ], [
-    PHP_CHECK_LIBRARY(gds, isc_detach_database,
+    PHP_CHECK_LIBRARY(fbclient, isc_detach_database,
     [
-      FIREBIRD_LIBNAME=gds
+      FIREBIRD_LIBNAME=fbclient
     ], [
-      PHP_CHECK_LIBRARY(ib_util, isc_detach_database,
+      PHP_CHECK_LIBRARY(gds, isc_detach_database,
       [
-        FIREBIRD_LIBNAME=ib_util
+        FIREBIRD_LIBNAME=gds
       ], [
-        AC_MSG_ERROR([libfbclient, libgds or libib_util not found! Check config.log for more information.])
+        PHP_CHECK_LIBRARY(ib_util, isc_detach_database,
+        [
+          FIREBIRD_LIBNAME=ib_util
+        ], [
+          AC_MSG_ERROR([libfbclient, libgds or libib_util not found! Check config.log for more information.])
+        ], [
+          $FIREBIRD_LIBDIR_FLAG
+        ])
       ], [
         $FIREBIRD_LIBDIR_FLAG
       ])
     ], [
       $FIREBIRD_LIBDIR_FLAG
     ])
-  ], [
-    $FIREBIRD_LIBDIR_FLAG
-  ])
+    PHP_ADD_LIBRARY_WITH_PATH($FIREBIRD_LIBNAME, $FIREBIRD_LIBDIR, PDO_FIREBIRD_SHARED_LIBADD)
+    PHP_ADD_INCLUDE($FIREBIRD_INCDIR)
+  fi
  
   PHP_CHECK_PDO_INCLUDES
 
-  PHP_ADD_LIBRARY_WITH_PATH($FIREBIRD_LIBNAME, $FIREBIRD_LIBDIR, PDO_FIREBIRD_SHARED_LIBADD)
-  PHP_ADD_INCLUDE($FIREBIRD_INCDIR)
   AC_DEFINE(HAVE_PDO_FIREBIRD,1,[ ])
   PHP_NEW_EXTENSION(pdo_firebird, pdo_firebird.c firebird_driver.c firebird_statement.c, $ext_shared,,-I$pdo_cv_inc_path)
   PHP_SUBST(PDO_FIREBIRD_SHARED_LIBADD)