ob handler should not print the output in case of callback exception

Description

The following code:

<?php

ob_start(function ($buffer) {
    // return '';
    throw new \Exception('x');
});

echo 5;

try {
    ob_flush();
} catch (\Exception $e) {
    echo $e;
}

Expected output:

-5Exception: x in /in/kQMfY:5
+Exception: x in /in/kQMfY:5
 Stack trace:
 #0 [internal function]: {closure}('5', 5)
 #1 /in/kQMfY(11): ob_flush()
 #2 {main}

https://3v4l.org/kQMfY

PHP Version

any

Operating System

any

Start by running the provided PHP reproduction for ob_start and ob_flush, then compare its output with the expected output and the linked 3v4l example. Trace the output-buffer callback exception path in php-src and verify that the buffered value 5 is not printed when the callback throws; the work is done when this behavior is covered by a regression test.