PHP PDO查询无需参数即可工作，但不能使用

Question

I have a very simple query that works when I don't use parameters. With parameters, it returns nothing. Someone else posted the same issue over here: Query with input parameters doesn't work whereas direct query works

However no one has answered it. Below is my code.

require_once('database.class.php');

class Plan extends Database {
    public function getBenefitAmounts($plan_id, $group_id, $level) {
        $sql = 'SELECT DISTINCT benefit FROM rates WHERE plan_id = :plan AND group_id IS NULL AND `level` = :lvl';
        $params = array(':plan'=>896, ':lvl'=>1);
        $this->sqlQuery($sql, $params);

        // $sql = 'SELECT DISTINCT benefit FROM rates WHERE plan_id = 896 AND group_id IS NULL AND `level` = 1';
        // $this->sqlQuery($sql);

        $results = $this->sth->fetchAll(PDO::FETCH_COLUMN);

        $options = '';
        foreach ($results as $value) {
            $options .= '<option value="' . $value . '">$' . $value . '</option>';
        }

        return $options;
    }
}

In the database class:

public function sqlQuery($sql, $values_to_bind=null) {

    $this->sth = $this->pdo->prepare($sql);

    if (isset($values_to_bind)) {
        foreach ($values_to_bind as $param => $value) {
            $this->sth->bindValue($param, $value);
        }
    }
    $success = $this->sth->execute();
    if (!$success) {
        $arr = $this->$sth->errorInfo();
        print_r($arr);
    }
}

The code commented out of the first code snippet works just fine, but with parameters, it returns nothing. The getBenefitAmounts function is called from another PHP file which is called using a JQuery get.

Answer 1

Did you try to add the third param which is optional for bindValue(). It can be something like PDO::PARAM_INT, PDO::PARAM_STR etc. Just try to debug and see if it helps.