无法计算成功执行的 mysqli 查询

Question

我想看看我的查询是否成功（好吧，虽然我成功地执行了插入查询）但是在第 25 行出现了这个错误："mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given "我已经检查了每一行，我什至使用mysqli_affected_rows 失败了。感谢任何帮助，这是我的代码：

<?php
   include "connection.php";  
   $fn = $_POST['first_name'];
   $ln = $_POST['last_name'];
   $uname = $_POST['username'];
   $pwd = $_POST['password'];
   $stat = $_POST['status'];  
   if($fn=="" || $ln=="" || $uname=="" || $pwd=="" || $stat==""){
     echo "ALL FIELD MUST BE FILLED!";
   }                                                                        
   else {
     $sql = "SELECT * from user WHERE username='$uname'";
     $result = mysqli_query($conn, $sql);
     $number = mysqli_num_rows($result);
   if ($number != 0) {
     echo "Username $uname is not available";
   }
   else {
     $options = ['cost' => 12];
     $pwd = password_hash($pwd, PASSWORD_BCRYPT, $options);
     $query = "INSERT INTO user 
              (username,password,first_name,last_name,status) VALUES 
              ('$uname','$pwd','$fn','$ln','$stat')";
     $res = mysqli_query($conn, $query);
     $nmb = mysqli_num_rows($res);

     echo $nmb;                                                             
    }                                                                         
  }                                                                         
?>

Answer 1

改变这个：

$res = mysqli_query($conn, $query);

$nmb = mysqli_num_rows($res);

echo $nmb;

为此：

$res = mysqli_query($conn, $query);
if ($res) { 
   echo "Insert ok";
}
else
{
   echo "Problem to insert";
}

Answer 2

$nmb = mysqli_num_rows($res); 无法工作，因为 $res 是 INSERT 查询的结果。 The documentation for mysqli_query 说：

Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object. For other successful queries mysqli_query() will return TRUE.

因此，$res 将始终是 false 或 true，您将无法使用 mysqli_num_rows() 或 mysqli_affected_rows()它。问题是，不管怎样，在这里计算行数并没有什么意义。您正在尝试插入一条记录，因此它要么是 1 要么是 0，因此 true 或 false 结果应该足以让您检测查询是否成功。

无法计算成功执行的 mysqli 查询

Cannot count successfully executed mysqli query

php

mysqli

insert-into