`MessageFormatter` uses default timezone to format dates

[MatTheCat]

Description

The following code:

<?php

date_default_timezone_set('UTC');

echo MessageFormatter::formatMessage(
    'fr_FR',
    '{datetime, time, short}',
    ['datetime' => new DateTimeImmutable('2023-03-27T12:00', new DateTimeZone('Europe/Paris'))]
);

Resulted in this output:

10:00

But I expected this output instead:

12:00

PHP Version

all

Operating System

No response

[damianwadley]

The main problem I see is that ICU's MessageFormatter doesn't seem to support this sort of behavior: internally, the date being passed for formatting is actually just a numeric timestamp. Which means there's a big question of what to do if you try to format a message with multiple DateTimes in different timezones...

I'm changing this to a feature request of having a way to specify the timezone on the MessageFormatter directly, instead of relying on PHP's default timezone with no way (that I saw) to change that.

[MatTheCat]

Okay I guess this won’t be simple to implement 😅

As a workaround I’ll pass datetimes as strings returned by IntlDateFormatter.

[heiglandreas]

I'd suggest to set the default timezone to Europe/Paris to get the correct result.

[MatTheCat]

In my case the timezone is dynamic so I cannot act on the server's.

[ndossche]

It is actually possible to fix this by including the timezone offset in the milliseconds. So this would already work if the default timezone is set to UTC:

diff --git a/ext/intl/common/common_date.cpp b/ext/intl/common/common_date.cpp
index e4f442a8195..1cf3e7da56c 100644
--- a/ext/intl/common/common_date.cpp
+++ b/ext/intl/common/common_date.cpp
@@ -113,9 +113,13 @@ U_CFUNC zend_result intl_datetime_decompose(zend_object *obj, double *millis, Ti
 
 	if (millis) {
 		auto getTimestampMethod = static_cast<zend_function *>(zend_hash_str_find_ptr(&obj->ce->function_table, ZEND_STRL("gettimestamp")));
+		auto getOffsetMethod = static_cast<zend_function *>(zend_hash_str_find_ptr(&obj->ce->function_table, ZEND_STRL("getoffset")));
 		zval retval;
+		double timestamp;
 
 		ZEND_ASSERT(getTimestampMethod && "DateTimeInterface is sealed and thus must have this method");
+		ZEND_ASSERT(getOffsetMethod && "DateTimeInterface is sealed and thus must have this method");
+
 		zend_call_known_function(getTimestampMethod, obj, obj->ce, &retval, 0, nullptr, nullptr);
 
 		/* An exception has occurred */
@@ -130,7 +134,25 @@ U_CFUNC zend_result intl_datetime_decompose(zend_object *obj, double *millis, Ti
 			return FAILURE;
 		}
 
-		*millis = U_MILLIS_PER_SECOND * (double)Z_LVAL(retval) + (datetime->time->us / 1000);
+		timestamp = (double) Z_LVAL(retval);
+
+		zend_call_known_function(getOffsetMethod, obj, obj->ce, &retval, 0, nullptr, nullptr);
+
+		/* An exception has occurred */
+		if (Z_TYPE(retval) == IS_UNDEF) {
+			return FAILURE;
+		}
+		// TODO: Remove this when DateTimeInterface::getoffset() no longer has a tentative return type
+		if (Z_TYPE(retval) != IS_LONG) {
+			spprintf(&message, 0, "%s: %s::getoffset() did not return an int", func, ZSTR_VAL(obj->ce->name));
+			intl_errors_set(err, U_INTERNAL_PROGRAM_ERROR, message, 1);
+			efree(message);
+			return FAILURE;
+		}
+
+		timestamp += (double) Z_LVAL(retval);
+
+		*millis = U_MILLIS_PER_SECOND * timestamp + (datetime->time->us / 1000);
 	}
 
 	if (tz) {

It's incomplete though because we need to not let the default timezone influence the output or the timezone offset will be added twice. Also needs a review of all other cases that this influences but jfc the intl code is a mess.