[php-src] Issue #12504: Corrupted session written when there's a fatal error in autoloader

Issue: https://github.com/php/php-src/issues/12504 Author: ssigwart ### Description Create two files in the same directory: index.php ```php <?php class TestSessionHandler implements SessionHandlerInterface { public function close(): bool { return true; } public function destroy($id): bool { return true; } public function gc($max_lifetime) { return 0; } public function open($path, $name): bool { return true; } public function read($id) { // Return a session object that has 3 variables return 'before|i:1234;test|O:4:"Test":0:{}after|i:5678;'; } public function write($id, $data): bool { echo 'Write session:' . PHP_EOL; echo $data . PHP_EOL; return true; } } session_set_save_handler(new TestSessionHandler()); // Autoload class that's in session spl_autoload_register(function() { require_once(__DIR__ . '/Test.class.php'); return true; }); // If you use this line, the session still fails to load, but the session will not be written back, which is ideal // require_once(__DIR__ . '/Test.class.php'); header('Content-type: text/plain'); session_start(); print_r($_SESSION); ``` **Test.class.php** ```php <?php class Test { // The = null results in a fatal error public int $var = null; } ``` When running index.php, it will result in a fatal error. However, it will also write a session with all variables before the invalid Test class set to zero and no variables after the $_SESSION['test']. You can see that in the output: ``` <br /> <b>Fatal error</b>: Default value for property of type int may not be null. Use the nullable type ?int to allow null default value in <b>/path/to/dir/Test.class.php</b> on line <b>5</b><br /> Write session: before|i:0; ``` If you uncomment the second require_once so that the autoloader doesn't need to run, it still results in the fatal error as expected, but it does not write back to the session. I know that avoiding the fatal error is a workaround, but if this can be fixed, it could prevent corrupting user sessions if bad code gets deployed to production. ### PHP Version PHP 8.0.30 ### Operating System _No response_