Segfault when running built-in PHP web server

foo.php

<?php
class Foo
{
    public function execute($log)
    {
        file_put_contents($log, "this is a log\n", FILE_APPEND);
    }
}

(new Foo())->execute('./mylog.txt');

run-from-cli.sh

$ php foo.php
$ cat mylog.txt
this is a log

run-from-webserver.sh

$ php -S localhost:8000
PHP 7.1.3 Development Server started at Mon Oct 16 17:07:16 2017
Listening on http://localhost:8000
Document root is /home/ramsey/foo
Press Ctrl-C to quit.
[Mon Oct 16 17:07:38 2017] ::1:56424 [200]: /foo.php
[1]    53968 segmentation fault  php -S localhost:8000

For reference, I don't get a segfault with the script using PHP 7.1.8 on macOS 10.12.6 (compiled from Homebrew).

$ php -S localhost:9090
PHP 7.1.8 Development Server started at Mon Oct 16 16:02:36 2017
Listening on http://localhost:9090
Document root is /Users/jeff/Projects/gists/php
Press Ctrl-C to quit.
[Mon Oct 16 16:02:47 2017] ::1:60583 [200]: /seg.php

$ cat mylog.txt 
this is a log