What potential pitfalls should be considered when upgrading from PHP 7.4 to PHP 8.0, specifically regarding functions like feof()?

When upgrading from PHP 7.4 to PHP 8.0, one potential pitfall to consider is the change in behavior of the `feof()` function. In PHP 8.0, `feof()` now requires a file handle as a parameter, whereas in PHP 7.4 it could be called without any arguments. To fix this issue, you need to pass a file handle to `feof()` when calling it in PHP 8.0.

// PHP 7.4
$file = fopen('example.txt', 'r');
while (!feof($file)) {
    echo fgets($file) . "\n";
}
fclose($file);

// PHP 8.0
$file = fopen('example.txt', 'r');
while (!feof($file)) {
    echo fgets($file) . "\n";
}
fclose($file);