Using phpword to merge two Mircrosoft Office Word .docx documents

How to combine or embed and insert another .docx file (Microsoft office docx word document) into another one using PHPWord

Joining two .docx document using php (phpword library)

$mainTemplateProcessor = new \PhpOffice\PhpWord\TemplateProcessor("file1");
//$mainTemplateProcessor ->setValue('var_name', $value);

$innerTemplateProcessor = new \PhpOffice\PhpWord\TemplateProcessor("file2");
//$innerTemplateProcessor->setValue('var2_name', $value2);

// extract internal xml from template that will be merged inside main template
$innerXml = $innerTemplateProcessor->gettempDocumentMainPart();
$innerXml = preg_replace('/^[\s\S]*<w:body>(.*)<\/w:body>.*/', '$1', $innerXml);

// remove tag containing header, footer, images
$innerXml = preg_replace('/<w:sectPr>.*<\/w:sectPr>/', '', $innerXml);

// inject internal xml inside main template
$mainXml = $mainTemplateProcessor->gettempDocumentMainPart();
$mainXml = preg_replace('/<\/w:body>/', '<w:p><w:r><w:br w:type="page" /><w:lastRenderedPageBreak/></w:r></w:p>' . $innerXml . '</w:body>', $mainXml);
$mainTemplateProcessor->settempDocumentMainPart($mainXml);

$mainTemplateProcessor->saveAs($result_file_name);

In order for the above code to work, you need to modify edit and add to the TemplateProcessor.php file those two functions:

public function gettempDocumentMainPart()
{
    return $this->tempDocumentMainPart;
}

public function settempDocumentMainPart($new)
{
    return $this->tempDocumentMainPart = $new;
}

This answer is based on the answer of @pfleu here: https://github.com/PHPOffice/PHPWord/issues/1130