Q:

Set File permission when creating directory

I have a script that stores files into a directory. The function creates a new directory every 7 days based on the current date (2018>March>week1,2,3, etc.). It works fantastically, but I need to set the directory permissions to 777 otherwise I run into issues. See the code below.
static function initStorageFileDirectory() {
    $filepath = 'storage/';

    $year  = date('Y');
    $month = date('F');
    $day   = date('j');
    $week  = '';
    $mode = 0777;

    if (!is_dir($filepath . $year)) {
        //create new folder
        mkdir($filepath[$mode] . $year);
    }

    if (!is_dir($filepath . $year . "/" . $month)) {
        //create new folder
        mkdir($filepath[$mode] . "$year/$month");
    }

    if ($day > 0 && $day <= 7)
        $week = 'week1';
    elseif ($day > 7 && $day <= 14)
        $week = 'week2';
    elseif ($day > 14 && $day <= 21)
        $week = 'week3';
    elseif ($day > 21 && $day <= 28)
        $week = 'week4';
    else
        $week = 'week5';

    if (!is_dir($filepath . $year . "/" . $month . "/" . $week)) {
        //create new folder
        mkdir($filepath[$mode] . "$year/$month/$week");
    }

    $filepath = $filepath . $year . "/" . $month . "/" . $week . "/";

    return $filepath;
}

As you can see, I set $mode. This probably isn't the best way to do this: with the [$mode] inserted it fails to create the directory altogether, but if I remove that bit of code from the mkdir($filepath.... it works great.

A:

mkdir($filepath[$mode] . $year);

This doesn't do what you think it does. It takes the character at index $mode from $filepath, appends $year to it, and creates a directory at the result (without explicitly setting permissions). Since $filepath doesn't have 512 characters in it (0777 is 511 in octal), $filepath[$mode] returns an empty string (with an "Uninitialized string offset" notice) and mkdir tries to create a directory at $year.
mkdir takes multiple arguments, the second of which is the mode:
mkdir($filepath . $year, $mode);

But mkdir's default mode is 0777, so if the directory permissions end up being different, your umask is getting in the way. You can set your umask to allow 0777 permissions, but it's easier and (possibly) safer to chmod the directory after creating it:
mkdir($filepath . $year);
chmod($filepath . $year, $mode);

