protected function openReader($filePath)
    {
        $this->zip = new \ZipArchive();

        if ($this->zip->open($filePath) === true) {
            $this->sharedStringsHelper = new SharedStringsHelper($filePath, $this->getOptions()->getTempFolder());

            if ($this->sharedStringsHelper->hasSharedStrings()) {
                // Extracts all the strings from the sheets for easy access in the future
                $this->sharedStringsHelper->extractSharedStrings();
            }

            $this->sheetIterator = new SheetIterator($filePath, $this->getOptions(), $this->sharedStringsHelper, $this->globalFunctionsHelper);
        } else {
            throw new IOException("Could not open $filePath for reading.");
        }
    }