How to create a pdf file from encoded string content - Codeigniter - php

Question

I am getting response from cURL which is an encoded string format of pdf(i guess) - see attached image.
I am getting pdf file if i directly put the url in browser. Since its asking for api credentials for viewing the pdf, its not user friendly and i am looking for another way to directly download the file.
So i am trying to get the string content of the pdf file with cURL and i am getting exactly what in the image attached(only small portion attached).
Using that string content, i tried to save it as a plain txt file and from there i tried to decode the string text and to create a pdf file newly. After creating i need to download the same.
I could create text file with the string data i got from cURL and could create pdf also. But the downloaded file showing Failed to load PDF document.
Below is the code i have tried and i am not sure whether i tried correctly or not.
function pdf_download(){
$this->load->helper('file');
$curl = $this->api_call->callapi('GET',APIURL."carts/96171/tickets");
$content = $curl;
$my_file = FCPATH . '/document/text.txt';
if (write_file($my_file, $content) == FALSE)
{
echo 'Unable to write the file';
}
else
{
echo 'File written!';
}
$pdf_base64 = $my_file;
//Get File content from txt file
$pdf_base64_handler = fopen($pdf_base64,'r');
$pdf_content = fread ($pdf_base64_handler,filesize($pdf_base64));
fclose ($pdf_base64_handler);
//Decode pdf content
$pdf_decoded = base64_decode ($pdf_content);
//Write data back to pdf file
$pdf_file=FCPATH . '/document/ticket.pdf';
$pdf = fopen ($pdf_file,'w');
fwrite ($pdf,$pdf_decoded);//Creating a pdf from the encoded content in txt file
fclose ($pdf);
header('Content-Type: application/octet-stream');
header("Content-Transfer-Encoding: Binary");
header("Content-disposition: attachment; filename=tickets.pdf");
ob_clean(); flush();
readfile($pdf_file);//downloading the pdf file
exit();
}

Answer 1

Since streaming a download to the browser requires sending headers, you must not output anything before sending headers. Therefore, you must get rid of:
if (write_file($my_file, $content) == FALSE)
{
echo 'Unable to write the file';
}
else
{
echo 'File written!';
}
If you definitely need to check if the file was written (for debugging purposes, I assume) you may use CI's log_message() to write a debug entry in the logs or just set a control variable. For example:
if (write_file($my_file, $content) == FALSE)
{
log_message('debug', "Unable to write file");
$file_written = false;
}
else
{
log_message('debug', "File succesfully written");
$file_written = true;
}
Also, there's some headers missing to ensure the file is not streamed to the browser but sent for download, as well as some required to make sure the file is correctly downloaded
header('Content-Description: File Transfer');
header('Content-Type: '. mime_content_type($pdf_file)); // since you're using Codeigniter, this will try to use the correct mimetype
header('Content-Disposition: attachment; filename="ticket.pdf"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($pdf_file));
readfile($pdf_file);

Answer 2

The wrong line in the above given code is $pdf_decoded = base64_decode ($pdf_content);.
It should be changed to $pdf_decoded = $pdf_content;
Since string in encoded format is already getting which is needed for creating PDF. So no need to decode it.
Also the above code is reduced as below.
function pdf_download(){
$this->load->helper('file');
$this->load->helper('download');
$cart_id=$this->input->get('cart_id');
$curl = $this->api_call->callapi('GET',APIURL."cart/'.$cart_id.'/tickets");
$pdf_file=FCPATH . 'document\voucher-'.$cart_id.'.pdf';
if (write_file($pdf_file, $curl))
{
force_download($pdf_file, NULL);
}
}