Php 警告：mysqli_query（）要求参数2为字符串，对象为给定的

有人能帮我解决这个错误吗

警告：mysqli_查询要求参数2为字符串，对象为给定。。第25行

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名为query的变量应仅为。。。质疑

$result=mysqli_query$con，从预订中选择*，其中r_date='.$date'

此外，即使您认为您将获得一条记录，也可以使用函数mysqli\u fetch\u array 将始终返回一个数组。因此，您需要选择数组中的第一项，然后选择键或索引

$price=$row[0]['combo_price']

一些代码实践。不要把所有的东西都放在你的IF里。因为如果失败，$payment将是未定义的，并抛出一个错误。在脚本上初始化它。您还需要存储mysqli_查询的返回值，因为您需要释放用于该查询的内存

mysqli_free_result$result

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您的代码有多个问题。丢失的重复调用mysqli_查询、SQL注入和无错误检查

而不是在文件顶部使用if enable exceptions检查查询是否成功。使用预先准备好的语句，最好是以面向对象的方式

session_start();
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); //  this line enables exceptions
include 'includes/dbcon.php';

$stmt = $con->prepare('SELECT * FROM reservation WHERE r_date=?'); // ? is a placeholder for binding data
$stmt->bind_param('s', $date); // bind data to SQL statement as a string(s)
$stmt->execute();
$reservations = $stmt->get_result();

// if your SELECT found some record then loop on the result set fetching each row one by one
while ($row = $reservations->fetch_assoc()) {
    $combos = $con->query("SELECT * FROM combo where combo_id=1"); // if there is no data to be bound then we can use query
    $row = $combos->fetch_assoc(); // fetch the matching combo row
    $price = $row['combo_price'];
    $payable = $pax * $price;
}

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什么是$query？定义在哪里？测试var$query，而不是if语句中的mysqli_查询操作您似乎缺少引号和；除了反复运行mysqli_query之外，我还假设您的意思是警告不冲突-两个复制/粘贴错误。

<?php 
session_start();
include('includes/dbcon.php');

// you're missing some syntax here.. 
// also your $query IS your query so it should be $query = "SELECT * FROM ";

$query = mysqli_query($con, "SELECT * FROM reservation WHERE r_date='".$date."'
// you don't need this above line.. it does it all right here...
if (!mysqli_query($con,$query))  
{
$query = mysqli_query($con, "SELECT * FROM combo where combo_id=1");
$row=mysqli_fetch_array($query);
$price=$row['combo_price'];
$payable=$pax*$price;
// missing closing brackets. }

session_start();
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); //  this line enables exceptions
include 'includes/dbcon.php';

$stmt = $con->prepare('SELECT * FROM reservation WHERE r_date=?'); // ? is a placeholder for binding data
$stmt->bind_param('s', $date); // bind data to SQL statement as a string(s)
$stmt->execute();
$reservations = $stmt->get_result();

// if your SELECT found some record then loop on the result set fetching each row one by one
while ($row = $reservations->fetch_assoc()) {
    $combos = $con->query("SELECT * FROM combo where combo_id=1"); // if there is no data to be bound then we can use query
    $row = $combos->fetch_assoc(); // fetch the matching combo row
    $price = $row['combo_price'];
    $payable = $pax * $price;
}