https://stackoverflow.com/questions/59220954/retrieving-pdf-

    <?php


$invoice = array(
    "logo" => "test.dev", // url to logo
    "from" => "Wouter van Marrum \n<a href=\"http://www.concept-core.nl\">concept-core.nl</a>", // The name of your organization
    "to" => "marleen", // The entity being billed - multiple lines ok
    "number" => 20001, // Invoice number
    //"purchase_order" => "", // Purchase order number
    "date" => null, // Invoice date
    "due_date" => null, // Invoice due date
    "payment_terms" => null, // Payment terms summary (i.e. NET 30)
    // items
    "items[0][name]" => "Website",
    "items[0][quantity]" => 1,
    "items[0][unit_cost]" => 300,
    "items[1][name]" => "logo",
    "items[1][quantity]" => 1,
    "items[1][unit_cost]" => 150,
    // End items
    // Fields
    "fields[tax]" => true, // can be true, false
    "fields[discounts]" => false, // Subtotal discounts - numbers only
    "fields[shipping]" => false, // Can be true or false
    // End fields
    "tax"=> 21, // Tax - numbers only
    "amount_paid" => 0, // Amount paid - numbers only
    "notes" => "", // Notes - any extra information not included elsewhere
    "terms" => "Lees dit", // Terms and conditions - all the details
);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://invoice-generator.com");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 ); // AGREGADO POR MI
curl_setopt($ch, CURLOPT_POSTFIELDS, $invoice);
$result = curl_exec($ch);

//header('Content-Length: ' . $response->getHeader('Content-Length')[0]);

//$file = $result->getBody();

header('Cache-Control: public');
header('Content-type: application/pdf');
header('Content-Disposition: attachment; filename="new.pdf"');
header('Content-Length: '.strlen($result));

echo $result;


curl_close($ch);