当前路径：Classes/PHPExcel/Writer/Excel2007/Rels.php
<?php

/**
 * PHPExcel_Writer_Excel2007_Rels
 *
 * Copyright (c) 2006 - 2015 PHPExcel
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package    PHPExcel_Writer_Excel2007
 * @copyright  Copyright (c) 2006 - 2015 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
 * @version    ##VERSION##, ##DATE##
 */
class PHPExcel_Writer_Excel2007_Rels extends PHPExcel_Writer_Excel2007_WriterPart
{
    /**
     * Write relationships to XML format
     *
     * @param     PHPExcel    $pPHPExcel
     * @return     string         XML Output
     * @throws     PHPExcel_Writer_Exception
     */
    public function writeRelationships(PHPExcel $pPHPExcel = null)
    {
        // Create XML writer
        $objWriter = null;
        if ($this->getParentWriter()->getUseDiskCaching()) {
            $objWriter = new PHPExcel_Shared_XMLWriter(PHPExcel_Shared_XMLWriter::STORAGE_DISK, $this->getParentWriter()->getDiskCachingDirectory());
        } else {
            $objWriter = new PHPExcel_Shared_XMLWriter(PHPExcel_Shared_XMLWriter::STORAGE_MEMORY);
        }

        // XML header
        $objWriter->startDocument('1.0', 'UTF-8', 'yes');

        // Relationships
        $objWriter->startElement('Relationships');
        $objWriter->writeAttribute('xmlns', 'http://schemas.openxmlformats.org/package/2006/relationships');

        $customPropertyList = $pPHPExcel->getProperties()->getCustomProperties();
        if (!empty($customPropertyList)) {
            // Relationship docProps/app.xml
            $this->writeRelationship(
                $objWriter,
                4,
                'http://schemas.openxmlformats.org/officeDocument/2006/relationships/custom-properties',
                'docProps/custom.xml'
            );

        }

        // Relationship docProps/app.xml
        $this->writeRelationship(
            $objWriter,
            3,
            'http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties',
            'docProps/app.xml'
        );

        // Relationship docProps/core.xml
        $this->writeRelationship(
            $objWriter,
            2,
            'http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties',
            'docProps/core.xml'
        );

        // Relationship xl/workbook.xml
        $this->writeRelationship(
            $objWriter,
            1,
            'http://schemas....