I am unable to load a PEM that was generated with the stunnel tools. However, I am able to use PHP calls to generate a working PEM that is recognized both by stunnel and php, as outlined here:

http://www.devdungeon.com/content/how-use-ssl-sockets-php

This code fragment is now working for me, and with stunnel verify=4, both sides confirm the fingerprint. Oddly, if "tls://" is set below, then TLSv1 is forced, but using "ssl://" allows TLSv1.2:

$stream_context = stream_context_create([ 'ssl' => [
'local_cert'        => '/path/to/key.pem',
'peer_fingerprint'  => openssl_x509_fingerprint(file_get_contents('/path/to/key.crt')),
'verify_peer'       => false,
'verify_peer_name'  => false,
'allow_self_signed' => true,
'verify_depth'      => 0 ]]);

$fp = stream_socket_client('ssl://ssl.server.com:12345',
   $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $stream_context);
fwrite($fp, "foo bar\n");
while($line = fgets($fp, 8192)) echo $line;