diff --git a/ext/enchant/config.m4 b/ext/enchant/config.m4
index 9613c29297df4..1054b5839b555 100644
--- a/ext/enchant/config.m4
+++ b/ext/enchant/config.m4
@@ -12,7 +12,8 @@ if test "$PHP_ENCHANT" != "no"; then
     PHP_EVAL_INCLINE([$ENCHANT2_CFLAGS])
     PHP_EVAL_LIBLINE([$ENCHANT2_LIBS], [ENCHANT_SHARED_LIBADD])
     AC_DEFINE([HAVE_ENCHANT_GET_VERSION], [1],
-      [enchant_get_version since 1.6.0])
+      [Define to 1 if Enchant library has the 'enchant_get_version' function
+      (available since 1.6.0).])
   ], [
     AC_MSG_WARN([libenchant-2 not found trying with old libenchant])
     PKG_CHECK_MODULES([ENCHANT], [enchant >= 1.4.2])
@@ -21,14 +22,14 @@ if test "$PHP_ENCHANT" != "no"; then
     PHP_EVAL_LIBLINE([$ENCHANT_LIBS], [ENCHANT_SHARED_LIBADD])
 
     PHP_CHECK_LIBRARY([enchant], [enchant_get_version],
-      [AC_DEFINE([HAVE_ENCHANT_GET_VERSION], [1],
-        [enchant_get_version since 1.6.0])],
+      [AC_DEFINE([HAVE_ENCHANT_GET_VERSION], [1])],
       [],
       [$ENCHANT_LIBS])
 
     PHP_CHECK_LIBRARY([enchant], [enchant_broker_set_param],
       [AC_DEFINE([HAVE_ENCHANT_BROKER_SET_PARAM], [1],
-        [enchant_broker_set_param since 1.5.0 and removed in 2.x])],
+        [Define to 1 if Enchant library has the 'enchant_broker_set_param'
+        function (available since 1.5.0 and removed in 2.x).])],
       [],
       [$ENCHANT_LIBS])
   ])
diff --git a/ext/enchant/config.w32 b/ext/enchant/config.w32
index 167f06c11c535..c50f48ffb6c81 100644
--- a/ext/enchant/config.w32
+++ b/ext/enchant/config.w32
@@ -9,7 +9,7 @@ if (PHP_ENCHANT == "yes") {
 			have_enchant = true;
 		} else if (CHECK_LIB("libenchant.lib", "enchant", PHP_ENCHANT)) {
 			have_enchant = true;
-			AC_DEFINE('HAVE_ENCHANT_BROKER_SET_PARAM', 1);
+			AC_DEFINE('HAVE_ENCHANT_BROKER_SET_PARAM', 1, "Define to 1 if Enchant library has the 'enchant_broker_set_param' function (available since 1.5.0 and removed in 2.x).");
 		} else {
 			have_enchant = false;
 			WARNING('Could not find libenchant.lib; skipping');
@@ -17,7 +17,7 @@ if (PHP_ENCHANT == "yes") {
 		if (have_enchant) {
 			EXTENSION("enchant", "enchant.c");
 			AC_DEFINE('HAVE_ENCHANT', 1, "Define to 1 if the PHP extension 'enchant' is available.");
-			AC_DEFINE('HAVE_ENCHANT_GET_VERSION', 1);
+			AC_DEFINE('HAVE_ENCHANT_GET_VERSION', 1, "Define to 1 if Enchant library has the 'enchant_get_version' function (available since 1.6.0).");
 		}
 	} else {
 		WARNING('Could not find enchant.h; skipping');
diff --git a/ext/snmp/config.m4 b/ext/snmp/config.m4
index 05d4b705a0a5d..28b2b0169c2d1 100644
--- a/ext/snmp/config.m4
+++ b/ext/snmp/config.m4
@@ -45,19 +45,24 @@ if test "$PHP_SNMP" != "no"; then
 
   dnl Check whether shutdown_snmp_logging() exists.
   PHP_CHECK_LIBRARY([$SNMP_LIBNAME], [shutdown_snmp_logging],
-    [AC_DEFINE([HAVE_SHUTDOWN_SNMP_LOGGING], [1], [ ])],
+    [AC_DEFINE([HAVE_SHUTDOWN_SNMP_LOGGING], [1],
+      [Define to 1 if SNMP library has the 'shutdown_snmp_logging' function.])],
     [],
     [$SNMP_SHARED_LIBADD])
 
   dnl Check whether usmHMAC192SHA256AuthProtocol exists.
   PHP_CHECK_LIBRARY([$SNMP_LIBNAME], [usmHMAC192SHA256AuthProtocol],
-    [AC_DEFINE([HAVE_SNMP_SHA256], [1], [ ])],
+    [AC_DEFINE([HAVE_SNMP_SHA256], [1],
+      [Define to 1 if SNMP library has the 'usmHMAC192SHA256AuthProtocol'
+      array.])],
     [],
     [$SNMP_SHARED_LIBADD])
 
   dnl Check whether usmHMAC384SHA512AuthProtocol exists.
   PHP_CHECK_LIBRARY([$SNMP_LIBNAME], [usmHMAC384SHA512AuthProtocol],
-    [AC_DEFINE([HAVE_SNMP_SHA512], [1], [ ])],
+    [AC_DEFINE([HAVE_SNMP_SHA512], [1],
+      [Define to 1 if SNMP library has the 'usmHMAC384SHA512AuthProtocol'
+      array.])],
     [],
     [$SNMP_SHARED_LIBADD])