openssl_x509_verify

<?php
$hostname = "news.php.net";
$ssloptions = array(
    "capture_peer_cert" => true, 
    "capture_peer_cert_chain" => true, 
    "allow_self_signed"=> false, 
    "CN_match" => $hostname,
    "verify_peer" => true,
    "SNI_enabled" => true,
    "SNI_server_name" => $hostname,
);
 
$ctx = stream_context_create( array("ssl" => $ssloptions) );
$result = stream_socket_client("ssl://$hostname:443", $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $ctx);
$cont = stream_context_get_params($result);
$x509 = $cont["options"]["ssl"]["peer_certificate"];
$certparsed = openssl_x509_parse($x509);

foreach($cont["options"]["ssl"]["peer_certificate_chain"] as $chaincert)
{
    $chainparsed = openssl_x509_parse($chaincert);
    $chain_public_key = openssl_get_publickey($chaincert);
    $r = openssl_x509_verify($x509, $chain_public_key);   
    if ($r==1)
    {
        echo $certparsed['subject']['CN'];
        echo " was digitally signed by ";
        echo $chainparsed['subject']['CN']."\n";
    }
}
?>