传递公钥，私钥和CA in stream_get_contents（）调用Multipart / Related

I am attempting to connect to a 3rd party API, and they require me to pass 3 certificate files they have given me: public cert, private cert, and CA cert. It works fine in cURL with the following settings:

if (empty($this->order['connector'])) {
    curl_setopt($_curl, CURLOPT_SSLKEY, API_PRIVATE_CERT);
    curl_setopt($_curl, CURLOPT_CAINFO, API_CA_CERT);
    curl_setopt($_curl, CURLOPT_SSLCERT, API_PUBLIC_CERT);
}

Each value passed is a path to a physical file on the server. This works fine.

With one request, however, I have to pass a header 'Content-Type: Multipart/Related; boundary="---BOUNDARY123456"' with a MIME message that contains an XML file and a Base64 encoded PDF. This fails with a 500 error on their end. And in researching this, I have seen cURL cannot properly handle Content-Type: Multipart/Related posts.

https://stackoverflow.com/a/25998544/3434084

So I have tried to send it using stream_get_contents(), but I get no response back. So I am thinking my cert data is wrong. How can I pass the same values I use in cURL via stream_get_contents()?

Here's the code:

$payload = '----=FB498299F0F50D2A190B3C
Content-Type: application/x-ofx

<?xml version="1.0" encoding="ISO-8859-1"?>
<?OFX OFXHEADER="200" VERSION="201" SECURITY="NONE" OLDFILEUID="NONE" NEWFILEUID="NONE"?>
<OFX>
        <SIGNONMSGSRQV1>
                <SONRQ>
                        <LANGUAGE>ENG</LANGUAGE>
                        <APPID>TWEEN</APPID>
                </SONRQ>
        </SIGNONMSGSRQV1>
        ...
</OFX>

----=FB498299F0F50D2A190B3C
Content-Type: application/pdf
Content-Transfer-Encoding: base64
Content-Location: full1_1559588546.pdf

JVBERi0xLjQKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3RoIDM...PRgo=
----=FB498299F0F50D2A190B3C' . "

";

$params = [
    'http' => [
        'method' => 'POST',
        'header' => 'Content-Type: Multipart/Related; boundary="----=FB498299F0F50D2A190B3C"',
        'content' => $payload
    ],
    'ssl'  => [
        'verify_peer' => true,
        'local_pk'    => API_PRIVATE_CERT,
        'cafile'      => API_CA_CERT,
        'local_cert'  => API_PUBLIC_CERT
    ]
];

$_stream = stream_context_create($params);
$response = @file_get_contents('https://blah/api/, FILE_TEXT, $_stream);

TIA!

try

$params = [
    "ssl"=>[
        "verify_peer"=> true,
        "verify_peer_name"=> true,
        "cafile" => "pem.pem",
    ],
];

$response = file_get_contents($URL, 0, stream_context_create($params)

It turns out my issues was with the original cURL code I had used that was failing. Here's the updated code I needed to use in this case to send multipart/related content via cURL, using the 3rd party's SSL certificate data provided to me to authenticate access.

$headers = [
    'Content-Type: Multipart/Related; boundary="--' . $this->api_boundary . '";type=text/xml'
];

$_curl = curl_init();
curl_setopt($_curl, CURLOPT_URL, $this->api_url);
curl_setopt($_curl, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($_curl, CURLOPT_SSLCERTTYPE, FALSE);
curl_setopt($_curl, CURLOPT_POSTFIELDS, $this->api_xml);
curl_setopt($_curl, CURLOPT_POST, TRUE);
curl_setopt($_curl, CURLOPT_HTTPHEADER, $headers);

// TLS items
curl_setopt($_curl, CURLOPT_SSLKEY, API_PRIVATE_CERT); // path to private cert in .pem format
curl_setopt($_curl, CURLOPT_CAINFO, API_CA_CERT); // path to CA cert in .pem format
curl_setopt($_curl, CURLOPT_SSLCERT, API_PUBLIC_CERT); // path to public cert in .pem format

// process
$response = curl_exec($_curl);

// check for errors
if (curl_error($_curl)) {
    // capture error here
}

$status   = curl_getinfo($_curl);
curl_close($_curl);