system/Database/Forge.php
protected function _createTableAttributes(array $attributes): string
	{
		$sql = '';

		foreach (array_keys($attributes) as $key)
		{
			if (is_string($key))
			{
				$sql .= ' ' . strtoupper($key) . ' ' . $this->db->escape($attributes[$key]);
			}
		}

		return $sql;
	}
protected function _createTableAttributes(array $attributes): string
	{
		$sql = '';

		foreach (array_keys($attributes) as $key)
		{
			if (is_string($key))
			{
				$sql .= ' ' . strtoupper($key) . ' ' . $this->db->escape($attributes[$key]);
			}
		}

		return $sql;
	}
CREATE TABLE attributes

@param array $attributes Associative array of table attributes

@return string