Q:

PHP output buffering (ob_start, ob_flush)

I used php output buffering earlier in order to create csv file from database, because i didn't want to create an existing file, just wanted to make content downloadable.
CSV is text-based file, so its easy to create this way, you set the header and flush the text content. But! What if, I want to create an exe from hex data? (The project is: I have an existing exe file and I want that users can write something inside a HTML textbox and I convert that to hex and exchange the old text to the new one)
Thanks.

A:

Use following code to download exe file by reading from hard disk.
<?php
$file = 'test.exe';

if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($file));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file));
    ob_clean();
    flush();
    readfile($file);
    exit;
}

A:

If you want to replace part of binary file, for example from 100th byte to 200th byte you could use substr() and str_pad():
$binFile = file_get_contents('/pathto/exec/file.exec');
$replacedBinFile = substr($binFile, 0, 100) . str_pad(substr($_POST['text'], 0, 100), 100, "\x00") . substr($binFile, 200);
file_put_contents('/pathto/exec/file_replaced.exec', $replacedBinFile);

