protected function getPrefixLength(array $strings)
	{
		$i      = 0;
		$len    = 0;
		$maxLen = min(array_map('strlen', $strings));
		while ($i < $maxLen)
		{
			$c = $strings[0][$i];
			foreach ($strings as $string)
			{
				if ($string[$i] !== $c)
				{
					break 2;
				}
			}
			$len = ++$i;
		}

		return $len;
	}