Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Reader/Xls.php
public function listWorksheetNames($pFilename)
    {
        File::assertFile($pFilename);

        $worksheetNames = [];

        // Read the OLE file
        $this->loadOLE($pFilename);

        // total byte size of Excel data (workbook global substream + sheet substreams)
        $this->dataSize = strlen($this->data);

        $this->pos = 0;
        $this->sheets = [];

        // Parse Workbook Global Substream
        while ($this->pos < $this->dataSize) {
            $code = self::getUInt2d($this->data, $this->pos);

            switch ($code) {
                case self::XLS_TYPE_BOF:
                    $this->readBof();

                    break;
                case self::XLS_TYPE_SHEET:
                    $this->readSheet();

                    break;
                case self::XLS_TYPE_EOF:
                    $this->readDefault();

                    break 2;
                default:
                    $this->readDefault();

                    break;
            }
        }

        foreach ($this->sheets as $sheet) {
            if ($sheet['sheetType'] != 0x00) {
                // 0x00: Worksheet, 0x02: Chart, 0x06: Visual Basic module
                continue;
            }

            $worksheetNames[] = $sheet['name'];
        }

        return $worksheetNames;
    }
public function listWorksheetNames($pFilename)
    {
        File::assertFile($pFilename);

        $worksheetNames = [];

        // Read the OLE file
        $this->loadOLE($pFilename);

        // total byte size of Excel data (workbook global substream + sheet substreams)
        $this->dataSize = strlen($this->data);

        $this->pos = 0;
        $this->sheets = [];

        // Parse Workbook Global Substream
        while ($this->pos < $this->dataSize) {
            $code = self::getUInt2d($this->data, $this->pos);

            switch ($code) {
                case self::XLS_TYPE_BOF:
                    $this->readBof();

                    break;
                case self::XLS_TYPE_SHEET:
                    $this->readSheet();

                    break;
                case self::XLS_TYPE_EOF:
                    $this->readDefault();

                    break 2;
                default:
                    $this->readDefault();

                    break;
            }
        }

        foreach ($this->sheets as $sheet) {
            if ($sheet['sheetType'] != 0x00) {
                // 0x00: Worksheet, 0x02: Chart, 0x06: Visual Basic module
                continue;
            }

            $worksheetNames[] = $sheet['name'];
        }

        return $worksheetNames;
    }
Reads names of the worksheets from a file, without parsing the whole file to a PhpSpreadsheet object.

@param string $pFilename

@throws Exception

@return array