How can the user resolve the "Warning: fgets(): supplied argument is not a valid stream resource" error in their PHP script?

The "Warning: fgets(): supplied argument is not a valid stream resource" error occurs when the argument provided to the fgets() function is not a valid file handle. To resolve this error, you need to ensure that the file is opened correctly using fopen() and that the file handle is passed to the fgets() function. Make sure to check if the file is successfully opened before attempting to read from it.

$file = fopen("example.txt", "r");

if ($file) {
    while (!feof($file)) {
        $line = fgets($file);
        echo $line;
    }
    fclose($file);
} else {
    echo "Error opening file.";
}