download multiple files via curl - php

Question

I have an array of many IDs.
Each ID is assigned to an invoice.
With this curl command I can start download the invoice as pdf:
// DOWNLOAD INVOICE
$curl = curl_init('https://app.invoiz.de/api/invoice/1234/download');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_HEADER, true);
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "GET");
curl_setopt($curl, CURLOPT_USERPWD, $apiKey . ":" . $secretApiKey);
curl_setopt($curl, CURLOPT_HTTPHEADER, array(
'Authorization: Bearer '.$token->token,
'accept: application/pdf'
));
$content = curl_exec($curl);
curl_close($curl);
header('Content-Type: application/pdf');
header('Content-Type: application/octet-stream');
header("Content-Transfer-Encoding: Binary");
header("Content-disposition: attachment; filename=\"Invoice 1234.pdf\"");
echo $content;
Now I would like to download all invoices as seperated pdf files and I tried this:
foreach ($ids as $id) {
// DOWNLOAD INVOICE
$curl = curl_init('https://app.invoiz.de/api/invoice/'.$id.'/download');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_HEADER, true);
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "GET");
curl_setopt($curl, CURLOPT_USERPWD, $apiKey . ":" . $secretApiKey);
curl_setopt($curl, CURLOPT_HTTPHEADER, array(
'Authorization: Bearer '.$token->token,
'accept: application/pdf'
));
$content = curl_exec($curl);
curl_close($curl);
header('Content-Type: application/pdf');
header('Content-Type: application/octet-stream');
header("Content-Transfer-Encoding: Binary");
header("Content-disposition: attachment; filename=\"Invoice".$id.".pdf\"");
echo $content;
}
Problem: This will generate only one pdf file with the last invoice ID from the loop.
Where is my mistake?