The culprit is that we're basically calling stat() on the
symlink[1], and take st_size as being the size of the symlinked
file[2], while it is not.

[1] <https://github.com/php/php-src/blob/php-7.2.21/sapi/cli/php_cli_server.c#L1382>
[2] <https://github.com/php/php-src/blob/php-7.2.21/sapi/cli/php_cli_server.c#L2050>

> […], while it is not.

Oh, I misread the POSIX standard.  Actually, stat()ing a symlink
is supposed to give the target's size, and that works fine on
Linux (<https://3v4l.org/0u1fj>).

Now let's take a step away from the reported issue, and analyse
PHP's stat() function, which is obviously closely related.

On Windows, stat() works as expected on ZTS builds, and also on
NTS builds as of PHP 7.4.0.  However, NTS builds on previous PHP
versions rely on GetFileAttributesEx() for which the symbolik link
behavior is documented[1]:

| If the path points to a symbolic link, the function returns
| attributes for the symbolic link.

This is apparently not the case for you, as well as for me (may
very well depend on the Windows version).

And now back to the issue at hand.  The stat(3) call in the
built-in Webserver is (correctly) mapped to php_sys_stat(), and as
such relies on GetFileAttributesEx() (regardless of ZTS/NTS);
therefore the reported behavior is only fixed as of PHP 7.4.0
(even on ZTS builds).

Given the invasive nature of the required fix, and that PHP 7.3 is
already late in its release cycle, I don't think that we want to
back-port the fix to that version (PHP 7.2 is already off the table
for regular bug fixes).  Therefore I'm changing this to doc issue.

[1] <https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfileattributesexa>