如何执行功能十次

Question

我正在尝试使用for循环将10条不同的记录插入数据库中，但它一直只插入最后一个生成的记录。我希望每个记录在每个循环中都插入到数据库中。 这是main.php代码

<?php
if(isset($_POST['generate_voucher_code'])){
    //generate the number of codes
    $number_to_generate = $_POST['gen_no'];
    //echo $number_to_generate;
    $v_cost = $_POST['amount'];
    if($v_cost <= 500){
        $dur = 15;
    }
    else{
        $dur = 60;
    }
    //generate voucher
    $date = date('y-m-dh:i:s'); 
      for($i=1;$i<$number_to_generate + 1;$i++){
      //Voucher code
      $v_code= substr(md5($date),0,5);
      //if voucher doesnt exist
      if(!$user->check_voucher_code($v_code)){
                //save code
            $admin->save_voucher($v_code,$dur);
        }
      }
}
?>
<div class="row">
 <div class="col-md-4"></div>
        <div class="col-md-4">
         <form method="POST" class="form-inline">
            <div class="form-group">
             <select name="gen_no" class="form-control">
            <?php 
     for($i=1;$i<11;$i++){?>
        <option value="<?php echo $i;?>"><?php echo $i;?></option>
        <?php }?>
            </select>
        </div>
        <div class="form-group">
            <button class="btn btn-success" name="generate_voucher_code" style="border-radius:0;">Generate voucher code</button>
        </div>
        </form>
        </div>

        </div>

这是具有保存凭证功能的管理类

<?php
class Admin{
    private $db;
     function __construct($dbcon){
        $this->db = $dbcon;
    }
    public function save_voucher($v_code,$dur){
        try{
$stmt = $this->db->prepare("INSERT INTO voucher_codes(voucher_code,duration)
            VALUES (:v_code,:dur)");
            $stmt->bindParam(':v_code',$v_code);
            $stmt->bindParam(':dur',$dur);
            $stmt->execute();
            return true;
        }
        catch(PDOException $e){
            echo $e->getMessage();
            return false;
        }
    }
}