PHP stream_socket_client OpenSSL error (unknown ca)

Hello, I'm having some problems connecting to a server using the following php script : <?php

    $context = stream_context_create();
    stream_context_set_option($context, 'ssl', 'local_cert', './cert.pem');
    stream_context_set_option($context, 'ssl', 'allow_self_signed', TRUE);
    stream_context_set_option($context, 'ssl', 'verify_peer', FALSE);

    $ctn = stream_socket_client('ssl://distant.server.com:987', $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $context);
    if($ctn) {
        print('Connected !');
    }

?> cert.pem is a self signed certificate that I generated a few days ago, it contains both RSA Key and Certificate and I have supplied the certificate to the distant server. When I launch the script I get the following errors : Warning: stream_socket_client(): SSL operation failed with code 1. OpenSSL Error messages: error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca in /path/to/my/test.php on line 7 As it is a self signed certificate there is no CA so I added the two lines :

    stream_context_set_option($context, 'ssl', 'allow_self_signed', TRUE);
    stream_context_set_option($context, 'ssl', 'verify_peer', FALSE);

but that did not fix the problem. This is my first script that connects through a socket using SSL, but I think that it doesn't even get out of the server because it doesn't like the certificate. Do you have any ideas about how I could get this working ? or maybe just point me in the right direction. If you need any more info please let me know. Thank you, Richard