The problem:

I am trying to read a binary file from my web server via PHP but it’s coming back with an incorrect encoding (I think, though I can’t be sure).

Why I am doing this is because I want to remove the need for the user to download a file and populate an <input>, instead I want to automate the process so the file is automatically retrieved via PHP and the contents are processed by the clientside JS. I know this seems counter-intuitive, but it’s a very specific use-case for flashing ESP chips from ESPTool-JS.

Example results:

The reason I think this is an encoding issue is because this is what I get when reading from a localfile (contents truncated):

x01x00x00x00ðx0Fÿ÷littlefs/

And this is what I get when reading the same file from the server:

x01x00x00x00�x0F��littlefs/

My PHP Code

When running locally I am using an <input type="file" /> element and when running on the server I am using this PHP code:

$filePath = "bins/" . $_REQUEST["file"];

if (file_exists($filePath)) {
    $fileContents = file_get_contents($filePath);

    if ($fileContents === false) {
        http_response_code(500);
        die('Failed to read file');
    }

    // Remove BOM if present
    $fileContents = preg_replace('/^xEFxBBxBF/', '', $fileContents);

    // Set appropriate headers
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="'.basename($filePath).'"');

    // Output the file contents
    echo $fileContents;
} else {
    http_response_code(404);
    die('File not found');
}

My PHP.ini:

Please note that my PHP.ini file is set to UTF-8 for both the default_charset and the internal_encoding settings.

I’ve been battling this for a long time now! Help, pretty please!! ^_^