Mysql错误'无效使用组函数'[重复]

Question

This question already has an answer here:

• Call to a member function bind_param() on a non-object [duplicate] 6 answers

I am trying to check which ID is less than 2 times in ID_REF field with the code below. Its a referral application where the ID can refer only 2 directs. Cheers

CODE

 $stmt = $conex->prepare("SELECT id FROM tb_modules WHERE count(id_ref) < ? ORDER BY id DESC LIMIT 1");



                        $stmt->bind_param("s", $n);
                        $n = 2;

                        $stmt->execute();

                        $stmt->store_result();
                        $numrows = $stmt->num_rows;


                         $stmt->bind_result($id);

                        //$stmt->fetch();

                        $stmt->close();

                        //echo $id.' '.'oi';
                        while ($stmt->fetch()) {
                        echo $id;
                        }


                    }

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Answer 1

Do the following:

var_dump($conex);
$stmt = $conex->prepare("SELECT id FROM tb_modules WHERE count(id_ref) < ? ORDER BY id DESC LIMIT 1");

var_dump($stmt)

This should shed some light on the matter. I'm betting the $stmt variable is bool or null.