What file format is dat? Function code of PHP mandatory file download function arbitrary file format

Copy the codeThe code is as follows:

/********************
*@file - path to file
*/
function force_download($file)
{
if ((isset($file))&&(file_exists($file))) {
header("Content-length: ".filesize($file));
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $file . '"');
readfile("$file");
} else {
echo "No file selected";
}
}

The above introduces what file format dat is. The function code of PHP's mandatory file download function is any file format, including what file format dat is. I hope it will be helpful to friends who are interested in PHP tutorials.