PhpOffice\PhpPresentation\Writer\PowerPoint2007\Relationships::writeRelationships PHP Method

    public function writeRelationships()
    {
        // Create XML writer
        $objWriter = new XMLWriter(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');
        // Relationship ppt/presentation.xml
        $this->writeRelationship($objWriter, 1, 'http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument', 'ppt/presentation.xml');
        // Relationship docProps/core.xml
        $this->writeRelationship($objWriter, 2, 'http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties', 'docProps/core.xml');
        // Relationship docProps/app.xml
        $this->writeRelationship($objWriter, 3, 'http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties', 'docProps/app.xml');
        // Relationship docProps/custom.xml
        $this->writeRelationship($objWriter, 4, 'http://schemas.openxmlformats.org/officeDocument/2006/relationships/custom-properties', 'docProps/custom.xml');
        $idxRelation = 5;
        // Thumbnail
        if ($this->getPresentation()->getPresentationProperties()->getThumbnailPath()) {
            $pathThumbnail = file_get_contents($this->getPresentation()->getPresentationProperties()->getThumbnailPath());
            $gdImage = imagecreatefromstring($pathThumbnail);
            if ($gdImage) {
                imagedestroy($gdImage);
                // Relationship docProps/thumbnail.jpeg
                $this->writeRelationship($objWriter, $idxRelation, 'http://schemas.openxmlformats.org/package/2006/relationships/metadata/thumbnail', 'docProps/thumbnail.jpeg');
            }
        }
        // ++$idxRelation
        $objWriter->endElement();
        // Return
        return $objWriter->getData();
    }