Description:
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stream_copy_to_stream() copies 0 bytes when $source is a socket

Reproduce code:
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$sockets = stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, 0);

fwrite($sockets[0], b"a");
stream_socket_shutdown($sockets[0], STREAM_SHUT_WR);

var_dump(stream_copy_to_stream($sockets[1], STDOUT));

Expected result:
----------------
int(1)
a

Actual result:
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int(0)