can be collected for the first time, and no array subscript is defined for the second error: 0 
 can be collected for the third time, so problems occur alternately. The 
 code is as follows, and there is no problem when log comes out. 
public function getOneTitle($content_html){
    //
    $content_rules = [
        "title" => array("title", "text")  //
    ];
    $content_ql = $this->ql->html($content_html)->rules($content_rules)->query();
    $query = $content_ql->getData();
    $data = $query->all();
    if(empty($query->all()[0])){
        Log::write("1>>>".$content_html."<<<<<1end");
        $html2 = $content_ql->getHtml();
        Log::write("2>>>".$html2."<<<<<2end");
        var_dump($data);
    }
    $content = $data[0]["title"];
    return $content;
}