[ojuschugh1]

Fixes #16910

The problem was that ps_fetch_time() and ps_fetch_datetime() only print second_part when decimals is 1 to 6, the check added for bug #76386. MariaDB reports AUTO_SEC_PART_DIGITS (39) when the precision isn't known up front, for example for FROM_UNIXTIME('1992.1'), so prepared statements dropped the fraction that the text protocol returns.

I made any decimals above 6, the not-fixed sentinel (39 in MariaDB, 31 in MySQL), print six digits when second_part is non-zero and none otherwise, as MariaDB Connector/C does for 39, which gives the same strings as the text protocol. ps_fetch_time() gets the same change, though on MariaDB 13.0.2 I only got 39 for FROM_UNIXTIME() (TIMESTAMP) results.

The test compares the text and binary protocol results and skips unless the server reports 39 for FROM_UNIXTIME(). It fails without the fix on MariaDB 13.0.2 and skips on MySQL 8.4.13, and the other ext/mysqli, ext/pdo_mysql and ext/mysqlnd tests give the same results with and without the fix on both servers.

[ojuschugh1]

Changed to treat every decimals value above 6 as unknown precision, after @9EOR9's note in #16910 that 39 is a sentinel (31 in MySQL). It still prints no fraction when second_part is 0, since that's what the text protocol returns for FROM_UNIXTIME('1992.0').

[anun333]

Quoted below: written with Claude, an LLM, as CONTRIBUTING.md asks us to mark. The builds and test runs behind it are on my machine; the commands to repeat them are under the fold.

Tested against MariaDB 12.3.3 with debug builds of PHP-8.4 (51808ac5478) without and with this branch (be41b58628e):

	Without the patch	With it
gh16910.phpt	FAIL	PASS
ext/mysqli/tests	440 passed, 12 failed, 34 skipped	441 passed, 12 failed, 34 skipped

So the server reports the 39 sentinel for FROM_UNIXTIME() on 12.3 as well as on the 13.0.2 you tested. The same 12 tests fail on both builds against MariaDB; the one extra pass is the new test.

How this was tested

Builds (Linux x86_64, gcc 13.3), the same for both trees:

./buildconf --force
./configure --enable-debug --with-mysqli --disable-cgi --disable-phpdbg --disable-fileinfo
make -j6

Server and tests:

docker run -d --name mariadb-test -e MARIADB_ROOT_PASSWORD=test -e MARIADB_DATABASE=test -p 127.0.0.1:33306:3306 mariadb:12.3.3
export MYSQL_TEST_HOST=127.0.0.1 MYSQL_TEST_PORT=33306 MYSQL_TEST_USER=root MYSQL_TEST_PASSWD=test MYSQL_TEST_DB=test
TEST_PHP_EXECUTABLE=sapi/cli/php sapi/cli/php run-tests.php -q -n ext/mysqli/tests

On that server, SELECT FROM_UNIXTIME('1992.1') over the text protocol gives 1970-01-01 00:33:12.100000.