function file_size($file_name)
{
    $file_type = array( 'K', 'M', 'G' );
    $size = filesize ( $file_name );
    for ( $t = 0; $size > 1024; $t++ ){
        $size /= 1024;
        $file_size = round ( $size, 1 ) . ' ' . $file_type[ $t ] . 'B';
    }
    if(empty($file_size)) return 0;
    else return $file_size;
}