diff --git a/ext/intl/config.m4 b/ext/intl/config.m4
index d60068e5ad4..c4c3c9b1d4c 100644
--- a/ext/intl/config.m4
+++ b/ext/intl/config.m4
@@ -36,14 +36,6 @@ if test "$PHP_INTL" != "no"; then
       intl_convert.c
       intl_error.c
       listformatter/listformatter_class.c
-      msgformat/msgformat_attr.c
-      msgformat/msgformat_class.c
-      msgformat/msgformat_data.c
-      msgformat/msgformat_format.c
-      msgformat/msgformat_parse.c
-      msgformat/msgformat.c
-      normalizer/normalizer_class.c
-      normalizer/normalizer_normalize.c
       php_intl.c
       resourcebundle/resourcebundle_class.c
       resourcebundle/resourcebundle_iterator.c
@@ -73,6 +65,14 @@ if test "$PHP_INTL" != "no"; then
     calendar/calendar_class.cpp \
     calendar/calendar_methods.cpp \
     calendar/gregoriancalendar_methods.cpp \
+    msgformat/msgformat_attr.cpp \
+    msgformat/msgformat_class.cpp \
+    msgformat/msgformat_data.cpp \
+    msgformat/msgformat_format.cpp \
+    msgformat/msgformat_parse.cpp \
+    msgformat/msgformat.cpp \
+    normalizer/normalizer_class.cpp \
+    normalizer/normalizer_normalize.cpp \
     breakiterator/breakiterator_class.cpp \
     breakiterator/breakiterator_iterators.cpp \
     breakiterator/breakiterator_methods.cpp \
diff --git a/ext/intl/config.w32 b/ext/intl/config.w32
index dcec448c462..fb3f0212729 100644
--- a/ext/intl/config.w32
+++ b/ext/intl/config.w32
@@ -48,20 +48,20 @@ if (PHP_INTL != "no") {
 				locale_methods.cpp \
 				", "intl");
 		ADD_SOURCES(configure_module_dirname + "/msgformat", "\
-				msgformat.c \
-				msgformat_attr.c \
-				msgformat_class.c \
-				msgformat_data.c \
-				msgformat_format.c \
+				msgformat.cpp \
+				msgformat_attr.cpp \
+				msgformat_class.cpp \
+				msgformat_data.cpp \
+				msgformat_format.cpp \
 				msgformat_helpers.cpp \
-				msgformat_parse.c \
+				msgformat_parse.cpp \
 				", "intl");
 		ADD_SOURCES(configure_module_dirname + "/grapheme", "\
                                 grapheme_string.c grapheme_util.c  \
                                 ", "intl");
 		ADD_SOURCES(configure_module_dirname + "/normalizer", "\
-				normalizer_class.c \
-				normalizer_normalize.c \
+				normalizer_class.cpp \
+				normalizer_normalize.cpp \
 				", "intl");
 		ADD_SOURCES(configure_module_dirname + "/dateformat", "\
 				dateformat.c \
diff --git a/ext/intl/locale/locale_methods.cpp b/ext/intl/locale/locale_methods.cpp
index 2cc47d5cc4e..fd8712b3b46 100644
--- a/ext/intl/locale/locale_methods.cpp
+++ b/ext/intl/locale/locale_methods.cpp
@@ -936,7 +936,7 @@ static int handleAppendResult( int result, smart_str* loc_name)
 * }}} */
 U_CFUNC PHP_FUNCTION(locale_compose)
 {
-	smart_str      	loc_name_s = {0};
+	smart_str      	loc_name_s = {NULL, 0};
 	smart_str *loc_name = &loc_name_s;
 	zval*			arr	= NULL;
 	HashTable*		hash_arr = NULL;
diff --git a/ext/intl/msgformat/msgformat.c b/ext/intl/msgformat/msgformat.cpp
similarity index 96%
rename from ext/intl/msgformat/msgformat.c
rename to ext/intl/msgformat/msgformat.cpp
index 4f0beaf2c05..a9e1f71bfc6 100644
--- a/ext/intl/msgformat/msgformat.c
+++ b/ext/intl/msgformat/msgformat.cpp
@@ -19,10 +19,12 @@
 #include <unicode/ustring.h>
 #include <unicode/umsg.h>
 
+extern "C" {
 #include "php_intl.h"
 #include "msgformat_class.h"
 #include "msgformat_data.h"
 #include "intl_convert.h"
+}
 
 /* {{{ */
 static int msgfmt_ctor(INTERNAL_FUNCTION_PARAMETERS)
@@ -99,7 +101,7 @@ static int msgfmt_ctor(INTERNAL_FUNCTION_PARAMETERS)
 /* }}} */
 
 /* {{{ Create formatter. */
-PHP_FUNCTION( msgfmt_create )
+U_CFUNC PHP_FUNCTION( msgfmt_create )
 {
 	object_init_ex( return_value, MessageFormatter_ce_ptr );
 	if (msgfmt_ctor(INTERNAL_FUNCTION_PARAM_PASSTHRU) == FAILURE) {
@@ -110,7 +112,7 @@ PHP_FUNCTION( msgfmt_create )
 /* }}} */
 
 /* {{{ MessageFormatter object constructor. */
-PHP_METHOD( MessageFormatter, __construct )
+U_CFUNC PHP_METHOD( MessageFormatter, __construct )
 {
 	const bool old_use_exception = INTL_G(use_exceptions);
 	const zend_long old_error_level = INTL_G(error_level);
@@ -127,7 +129,7 @@ PHP_METHOD( MessageFormatter, __construct )
 /* }}} */
 
 /* {{{ Get formatter's last error code. */
-PHP_FUNCTION( msgfmt_get_error_code )
+U_CFUNC PHP_FUNCTION( msgfmt_get_error_code )
 {
 	zval*                    object  = NULL;
 	MessageFormatter_object*  mfo     = NULL;
@@ -147,7 +149,7 @@ PHP_FUNCTION( msgfmt_get_error_code )
 /* }}} */
 
 /* {{{ Get text description for formatter's last error code. */
-PHP_FUNCTION( msgfmt_get_error_message )
+U_CFUNC PHP_FUNCTION( msgfmt_get_error_message )
 {
 	zend_string*             message = NULL;
 	zval*                    object  = NULL;
diff --git a/ext/intl/msgformat/msgformat_attr.c b/ext/intl/msgformat/msgformat_attr.cpp
similarity index 96%
rename from ext/intl/msgformat/msgformat_attr.c
rename to ext/intl/msgformat/msgformat_attr.cpp
index 6d1813f4608..e7ec006e5e7 100644
--- a/ext/intl/msgformat/msgformat_attr.c
+++ b/ext/intl/msgformat/msgformat_attr.cpp
@@ -16,15 +16,17 @@
 #include <config.h>
 #endif
 
+extern "C" {
 #include "php_intl.h"
 #include "msgformat_class.h"
 #include "msgformat_data.h"
 #include "intl_convert.h"
+}
 
 #include <unicode/ustring.h>
 
 /* {{{ Get formatter pattern. */
-PHP_FUNCTION( msgfmt_get_pattern )
+U_CFUNC PHP_FUNCTION( msgfmt_get_pattern )
 {
 	MSG_FORMAT_METHOD_INIT_VARS;
 
@@ -46,7 +48,7 @@ PHP_FUNCTION( msgfmt_get_pattern )
 /* }}} */
 
 /* {{{ Set formatter pattern. */
-PHP_FUNCTION( msgfmt_set_pattern )
+U_CFUNC PHP_FUNCTION( msgfmt_set_pattern )
 {
 	char*       value = NULL;
 	size_t      value_len = 0;
@@ -105,7 +107,7 @@ PHP_FUNCTION( msgfmt_set_pattern )
 /* }}} */
 
 /* {{{ Get formatter locale. */
-PHP_FUNCTION( msgfmt_get_locale )
+U_CFUNC PHP_FUNCTION( msgfmt_get_locale )
 {
 	char *loc;
 	MSG_FORMAT_METHOD_INIT_VARS;
diff --git a/ext/intl/msgformat/msgformat_class.c b/ext/intl/msgformat/msgformat_class.cpp
similarity index 87%
rename from ext/intl/msgformat/msgformat_class.c
rename to ext/intl/msgformat/msgformat_class.cpp
index 4e0766a911b..e762febf0d1 100644
--- a/ext/intl/msgformat/msgformat_class.c
+++ b/ext/intl/msgformat/msgformat_class.cpp
@@ -14,10 +14,12 @@
 
 #include <unicode/unum.h>
 
+extern "C" {
 #include "msgformat_class.h"
 #include "php_intl.h"
 #include "msgformat_data.h"
 #include "msgformat_arginfo.h"
+}
 
 #include <zend_exceptions.h>
 
@@ -29,7 +31,7 @@ static zend_object_handlers MessageFormatter_handlers;
  */
 
 /* {{{ MessageFormatter_objects_free */
-void MessageFormatter_object_free( zend_object *object )
+U_CFUNC void MessageFormatter_object_free( zend_object *object )
 {
 	MessageFormatter_object* mfo = php_intl_messageformatter_fetch_object(object);
 
@@ -40,11 +42,11 @@ void MessageFormatter_object_free( zend_object *object )
 /* }}} */
 
 /* {{{ MessageFormatter_object_create */
-zend_object *MessageFormatter_object_create(zend_class_entry *ce)
+U_CFUNC zend_object *MessageFormatter_object_create(zend_class_entry *ce)
 {
 	MessageFormatter_object*     intern;
 
-	intern = zend_object_alloc(sizeof(MessageFormatter_object), ce);
+	intern = reinterpret_cast<MessageFormatter_object *>(zend_object_alloc(sizeof(MessageFormatter_object), ce));
 	msgformat_data_init( &intern->mf_data );
 	zend_object_std_init( &intern->zo, ce );
 	object_properties_init(&intern->zo, ce);
@@ -54,7 +56,7 @@ zend_object *MessageFormatter_object_create(zend_class_entry *ce)
 /* }}} */
 
 /* {{{ MessageFormatter_object_clone */
-zend_object *MessageFormatter_object_clone(zend_object *object)
+U_CFUNC zend_object *MessageFormatter_object_clone(zend_object *object)
 {
 	MessageFormatter_object     *mfo = php_intl_messageformatter_fetch_object(object);
 	zend_object             *new_obj = MessageFormatter_ce_ptr->create_object(object->ce);
@@ -66,7 +68,7 @@ zend_object *MessageFormatter_object_clone(zend_object *object)
 	/* clone formatter object */
 	if (MSG_FORMAT_OBJECT(mfo) != NULL) {
 		UErrorCode error = U_ZERO_ERROR;
-		MSG_FORMAT_OBJECT(new_mfo) = umsg_clone(MSG_FORMAT_OBJECT(mfo), &error);
+		MSG_FORMAT_OBJECT(new_mfo) = reinterpret_cast<UMessageFormat *>(umsg_clone(MSG_FORMAT_OBJECT(mfo), &error));
 
 		if (U_FAILURE(error)) {
 			zend_throw_error(NULL, "Failed to clone MessageFormatter");
diff --git a/ext/intl/msgformat/msgformat_data.c b/ext/intl/msgformat/msgformat_data.cpp
similarity index 92%
rename from ext/intl/msgformat/msgformat_data.c
rename to ext/intl/msgformat/msgformat_data.cpp
index 5d170d25945..f8b7ec39601 100644
--- a/ext/intl/msgformat/msgformat_data.c
+++ b/ext/intl/msgformat/msgformat_data.cpp
@@ -24,7 +24,7 @@
 /* {{{ void msgformat_data_init( msgformat_data* mf_data )
  * Initialize internals of msgformat_data.
  */
-void msgformat_data_init( msgformat_data* mf_data )
+U_CFUNC void msgformat_data_init( msgformat_data* mf_data )
 {
 	if( !mf_data )
 		return;
@@ -40,7 +40,7 @@ void msgformat_data_init( msgformat_data* mf_data )
 /* {{{ void msgformat_data_free( msgformat_data* mf_data )
  * Clean up memory allocated for msgformat_data
  */
-void msgformat_data_free(msgformat_data* mf_data)
+U_CFUNC void msgformat_data_free(msgformat_data* mf_data)
 {
 	if (!mf_data)
 		return;
@@ -69,7 +69,7 @@ void msgformat_data_free(msgformat_data* mf_data)
  */
 msgformat_data* msgformat_data_create( void )
 {
-	msgformat_data* mf_data = ecalloc( 1, sizeof(msgformat_data) );
+	msgformat_data* mf_data = reinterpret_cast<msgformat_data *>(ecalloc( 1, sizeof(msgformat_data) ));
 
 	msgformat_data_init( mf_data );
 
diff --git a/ext/intl/msgformat/msgformat_data.h b/ext/intl/msgformat/msgformat_data.h
index 539c7d6d925..bac94cbec34 100644
--- a/ext/intl/msgformat/msgformat_data.h
+++ b/ext/intl/msgformat/msgformat_data.h
@@ -17,7 +17,13 @@
 
 #include <php.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 #include "../intl_error.h"
+#ifdef __cplusplus
+}
+#endif
 
 #include <unicode/umsg.h>
 
@@ -26,16 +32,22 @@ typedef struct {
 	intl_error      error;
 
 	// formatter handling
-	UMessageFormat* umsgf;
+	UMessageFormat *umsgf;
 	char*			orig_format;
 	zend_ulong		orig_format_len;
 	HashTable*		arg_types;
 	int				tz_set; /* if we've already the time zone in sub-formats */
 } msgformat_data;
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 msgformat_data* msgformat_data_create( void );
 void msgformat_data_init( msgformat_data* mf_data );
 void msgformat_data_free( msgformat_data* mf_data );
+#ifdef __cplusplus
+}
+#endif
 
 #ifdef MSG_FORMAT_QUOTE_APOS
 int msgformat_fix_quotes(UChar **spattern, uint32_t *spattern_len, UErrorCode *ec);
diff --git a/ext/intl/msgformat/msgformat_format.c b/ext/intl/msgformat/msgformat_format.cpp
similarity index 97%
rename from ext/intl/msgformat/msgformat_format.c
rename to ext/intl/msgformat/msgformat_format.cpp
index 54babc98396..8e3ec28b389 100644
--- a/ext/intl/msgformat/msgformat_format.c
+++ b/ext/intl/msgformat/msgformat_format.cpp
@@ -18,11 +18,13 @@
 
 #include <unicode/ustring.h>
 
+extern "C" {
 #include "php_intl.h"
 #include "msgformat_class.h"
 #include "msgformat_data.h"
 #include "msgformat_helpers.h"
 #include "intl_convert.h"
+}
 
 #ifndef Z_ADDREF_P
 #define Z_ADDREF_P(z) ((z)->refcount++)
@@ -48,7 +50,7 @@ static void msgfmt_do_format(MessageFormatter_object *mfo, zval *args, zval *ret
 /* }}} */
 
 /* {{{ Format a message. */
-PHP_FUNCTION( msgfmt_format )
+U_CFUNC PHP_FUNCTION( msgfmt_format )
 {
 	zval *args;
 	MSG_FORMAT_METHOD_INIT_VARS;
@@ -69,7 +71,7 @@ PHP_FUNCTION( msgfmt_format )
 /* }}} */
 
 /* {{{ Format a message. */
-PHP_FUNCTION( msgfmt_format_message )
+U_CFUNC PHP_FUNCTION( msgfmt_format_message )
 {
 	zval       *args;
 	UChar      *spattern = NULL;
diff --git a/ext/intl/msgformat/msgformat_parse.c b/ext/intl/msgformat/msgformat_parse.cpp
similarity index 97%
rename from ext/intl/msgformat/msgformat_parse.c
rename to ext/intl/msgformat/msgformat_parse.cpp
index 5c4f0443981..28d7ce71080 100644
--- a/ext/intl/msgformat/msgformat_parse.c
+++ b/ext/intl/msgformat/msgformat_parse.cpp
@@ -18,11 +18,13 @@
 
 #include <unicode/ustring.h>
 
+extern "C" {
 #include "php_intl.h"
 #include "msgformat_class.h"
 #include "msgformat_data.h"
 #include "msgformat_helpers.h"
 #include "intl_convert.h"
+}
 
 /* {{{ */
 static void msgfmt_do_parse(MessageFormatter_object *mfo, char *source, size_t src_len, zval *return_value)
@@ -52,7 +54,7 @@ static void msgfmt_do_parse(MessageFormatter_object *mfo, char *source, size_t s
 /* }}} */
 
 /* {{{ Parse a message */
-PHP_FUNCTION( msgfmt_parse )
+U_CFUNC PHP_FUNCTION( msgfmt_parse )
 {
 	char *source;
 	size_t source_len;
@@ -74,7 +76,7 @@ PHP_FUNCTION( msgfmt_parse )
 /* }}} */
 
 /* {{{ Parse a message. */
-PHP_FUNCTION( msgfmt_parse_message )
+U_CFUNC PHP_FUNCTION( msgfmt_parse_message )
 {
 	UChar      *spattern = NULL;
 	int         spattern_len = 0;
diff --git a/ext/intl/normalizer/normalizer_class.c b/ext/intl/normalizer/normalizer_class.cpp
similarity index 86%
rename from ext/intl/normalizer/normalizer_class.c
rename to ext/intl/normalizer/normalizer_class.cpp
index d9e413d5e51..3838f754632 100644
--- a/ext/intl/normalizer/normalizer_class.c
+++ b/ext/intl/normalizer/normalizer_class.cpp
@@ -12,11 +12,22 @@
    +----------------------------------------------------------------------+
  */
 
+#if __cplusplus >= 201703L
+#include <string_view>
+#endif
+#include <unicode/unistr.h>
+
 #include "normalizer.h"
 #include "normalizer_class.h"
 #include "php_intl.h"
+#ifdef __cplusplus
+extern "C" {
+#endif
 #include "normalizer_arginfo.h"
 #include "intl_error.h"
+#ifdef __cplusplus
+}
+#endif
 
 #include <unicode/unorm.h>
 
@@ -29,7 +40,7 @@ zend_class_entry *Normalizer_ce_ptr = NULL;
 /* {{{ normalizer_register_Normalizer_class
  * Initialize 'Normalizer' class
  */
-void normalizer_register_Normalizer_class( void )
+U_CFUNC void normalizer_register_Normalizer_class( void )
 {
 	/* Create and register 'Normalizer' class. */
 	Normalizer_ce_ptr = register_class_Normalizer();
diff --git a/ext/intl/normalizer/normalizer_class.h b/ext/intl/normalizer/normalizer_class.h
index 6e57cae40ba..8f88f215abc 100644
--- a/ext/intl/normalizer/normalizer_class.h
+++ b/ext/intl/normalizer/normalizer_class.h
@@ -36,6 +36,12 @@ typedef struct {
 #define NORMALIZER_ERROR_CODE(co)   INTL_ERROR_CODE(NORMALIZER_ERROR(co))
 #define NORMALIZER_ERROR_CODE_P(co) &(INTL_ERROR_CODE(NORMALIZER_ERROR(co)))
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 void normalizer_register_Normalizer_class( void );
+#ifdef __cplusplus
+}
+#endif
 extern zend_class_entry *Normalizer_ce_ptr;
 #endif // #ifndef NORMALIZER_CLASS_H
diff --git a/ext/intl/normalizer/normalizer_normalize.c b/ext/intl/normalizer/normalizer_normalize.cpp
similarity index 97%
rename from ext/intl/normalizer/normalizer_normalize.c
rename to ext/intl/normalizer/normalizer_normalize.cpp
index 670042f34d2..92e8f1166ad 100644
--- a/ext/intl/normalizer/normalizer_normalize.c
+++ b/ext/intl/normalizer/normalizer_normalize.cpp
@@ -16,11 +16,18 @@
 #include <config.h>
 #endif
 
+#if __cplusplus >= 201703L
+#include <string_view>
+#include <unicode/unistr.h>
+#endif
+
+extern "C" {
 #include "php_intl.h"
 #include <unicode/unorm2.h>
 #include "normalizer.h"
 #include "normalizer_class.h"
 #include "intl_convert.h"
+}
 #include <unicode/utf8.h>
 
 
@@ -71,7 +78,7 @@ static UBool intl_is_normalized(zend_long form, const UChar *uinput, int32_t uin
 }/*}}}*/
 
 /* {{{ Normalize a string. */
-PHP_FUNCTION( normalizer_normalize )
+U_CFUNC PHP_FUNCTION( normalizer_normalize )
 {
 	char*			input = NULL;
 	/* form is optional, defaults to FORM_C */
@@ -200,7 +207,7 @@ PHP_FUNCTION( normalizer_normalize )
 /* }}} */
 
 /* {{{ Test if a string is in a given normalization form. */
-PHP_FUNCTION( normalizer_is_normalized )
+U_CFUNC PHP_FUNCTION( normalizer_is_normalized )
 {
 	char*	 	input = NULL;
 	/* form is optional, defaults to FORM_C */
@@ -276,7 +283,7 @@ PHP_FUNCTION( normalizer_is_normalized )
 /* }}} */
 
 /* {{{ Returns the Decomposition_Mapping property for the given UTF-8 encoded code point. */
-PHP_FUNCTION( normalizer_get_raw_decomposition )
+U_CFUNC PHP_FUNCTION( normalizer_get_raw_decomposition )
 {
 	char* input = NULL;
 	size_t input_length = 0;