Ошибка в коде PHP скрипта. Что делать?

Notice: Undefined index: offset_file in C:\xampp1\htdocs\ali\Classes\Reader.php on line 43

Warning: file(C:\xampp1\htdocs\ali\): failed to open stream: No such file or directory in C:\xampp1\htdocs\ali\Classes\Reader.php on line 44

Warning: file(C:\xampp1\htdocs\ali\): failed to open stream: No such file or directory in C:\xampp1\htdocs\ali\Classes\Reader.php on line 45

Warning: file_put_contents(C:\xampp1\htdocs\ali\): failed to open stream: No such file or directory in C:\xampp1\htdocs\ali\Classes\Reader.php on line 59Notice: Undefined index: offset_file in C:\xampp1\htdocs\ali\Classes\Reader.php on line 43

Warning: file(C:\xampp1\htdocs\ali\): failed to open stream: No such file or directory in C:\xampp1\htdocs\ali\Classes\Reader.php on line 44

Warning: file(C:\xampp1\htdocs\ali\): failed to open stream: No such file or directory in C:\xampp1\htdocs\ali\Classes\Reader.php on line 45

Warning: file_put_contents(C:\xampp1\htdocs\ali\): failed to open stream: No such file or directory in C:\xampp1\htdocs\ali\Classes\Reader.php on line 59

P.S. строка 43 ___		$f2= str_replace('Classes/', '', __DIR__.'/'.$this->config['offset_file']);

public function getPostStrs($filename)
	{
		$filename = str_replace('Classes/', '', __DIR__.'/'.$filename);
		$f2= str_replace('Classes/', '', __DIR__.'/'.$this->config['offset_file']);
		$array = file($filename);
		$offset = (int) file($f2)[0];
		if ($offset+450 > count($array)) {
			$offset = 0;
		}
		$str = '';
		$j = 0;
		for ($i = 0; $i < 455; $i++) {
			if ($i > 4 && $i < 8) {
				$str.="\n ";
				continue;
			}
			$str.=$array[$offset+$j];
			$j++;
		}
		file_put_contents($f2, $offset+$j);
		return $str;
	}