pdo：从数据库收集数据[重复]

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I'm new to php..I'm trying to collect question from database

I figure out that error appear when the reture from fetchColum is false

Fatal error: Call to a member function fetchColumn() on boolean

    //////// Collected from databse ///////
$question_id=$question_id+1;


//$no_questions = $dbo->query("select count(qst_id) from poll_qst")->fetchColumn();
$no_questions = $dbo->query("select count(question) from questions
                    left join servey_question on questions.question_id = servey_question.question_id where servey_id = serv01 ")->fetchColumn();

print("name = $no_questions
");


if($question_id > $no_questions){

$next='F'; // Flag is set to display thank you message

}else{

$next='T'; // Flag is set to display next question



$count=$dbo->prepare("select * from questions where question_id=$question_id");

if($count->execute()){

$row = $count->fetch(PDO::FETCH_OBJ);

    }
}
$main= array("data"=>array("q1"=>"$row->question","opt1"=>"$row->opt1","opt2"=>"$row->opt2","opt3"=>"$row->opt3","opt4"=>"$row->opt4","opt5"=>"$row->opt5","opt6"=>"$row->opt6","question_id"=>"$question_id"),"next"=>"$next");
// end of collection from database //////


echo json_encode($main);

my Question is why I get false as result

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