<w:ffData> 
 <w:checkBox> 
 <w:size w:val="20" /> 
 <w:checked w:val="true" /> 
 </w:checkBox> 
</w:ffData> 

/**
 * Extend setCheckbox so it allows for the <w:checkBox> and <w:checked> tag within <w::ffData>
 * @see https://learn.microsoft.com/en-us/dotnet/api/documentformat.openxml.wordprocessing.checkbox?view=openxml-3.0.1#remarks
 * @see https://learn.microsoft.com/en-us/dotnet/api/documentformat.openxml.wordprocessing.checked?view=openxml-3.0.1#remarks
 * @param string $search
 * @param bool $checked
 * @return void
 */
 public function setCheckbox(string $search, bool $checked): void
 {
 parent::setCheckbox($search, $checked);
 $search = parent::ensureMacroCompleted($search);
 $blockType = 'w:ffData';
 $where = $this->findContainingXmlBlockForMacro($search, $blockType);
 if (!is_array($where)) {
 return;
 }
 $checkbox_end_tag = '</w:checkBox>';
 $block = $this->getSlice($where['start'], $where['end']);
 // test if the block contains the <w:checkBox> tag
 if (!is_string($block) || !str_contains($block, $checkbox_end_tag)) {
 return;
 }
 $val = $checked ? 'true' : 'false';
 $block = preg_replace('@(<w:checked w:val=)".*?"(/>)@', '1ドル"'.$val.'"2ドル', $block, -1, $checked_replaced);
 // in case there is a <w:checked/> tag, then above does not match.
 // this shouldn't happen, but still, don't trust spreadsheet clients too much
 if (!$checked_replaced) {
 $checked_tag = '<w:checked w:val="'.$val.'" />';
 $block = preg_replace('@<w:checked[^>]*>@', $checked_tag, $block, -1, $checked_replaced);
 }
 // the <w:checked> tag is not always present and is being added on first change.
 if (!$checked_replaced) {
 // there is no checked tag yet, so we add it
 $block = str_replace($checkbox_end_tag, $checked_tag.$checkbox_end_tag, $block);
 }
 $this->replaceXmlBlock($search, $block, $blockType);
 }