Built-in server leaks a file descriptor on every HEAD request for a static file

Description

Since PHP 8.2 (#8215), php_cli_server_begin_send_static() in sapi/cli/php_cli_server.c opens the static file but only stores the descriptor in client->file_fd for non-HEAD requests:

fd = open(client->request.path_translated, O_RDONLY);
...
if (client->request.request_method != PHP_HTTP_HEAD) {
    client->file_fd = fd;
}

For HEAD, fd is never stored and never closed. Each HEAD request to a static file leaks one descriptor; once RLIMIT_NOFILE is reached every request fails with 404 ... Too many open files. A monitoring probe doing HEAD / every 40 s takes down php -S in ~11 hours.

Affected: PHP-8.2, PHP-8.3, PHP-8.4, PHP-8.5, master. PHP 8.1 is not affected (no HEAD special-casing).

Reproduction:

mkdir t && echo hi > t/index.html
php -S 127.0.0.1:8080 -t t &
for i in $(seq 100); do curl -sI http://127.0.0.1:8080/ >/dev/null; done
ls -l /proc/$!/fd | grep -c index.html   # 100

Suggested fix — close the descriptor when it is not handed to the content sender (Content-Length uses client->request.sb.st_size from the earlier stat, so the fd is not needed for HEAD at all):

if (client->request.request_method != PHP_HTTP_HEAD) {
    client->file_fd = fd;
} else {
    close(fd);
}

PHP Version

PHP 8.2 – 8.5, master

Operating System

Linux (any)

Start in sapi/cli/php_cli_server.c at php_cli_server_begin_send_static(), then run the provided php -S and repeated curl HEAD reproduction. Done means repeated HEAD requests to a static file no longer increase open file descriptors, while normal static responses continue to work.