mysqli_query期望参数1为mysqli，给定布尔值

Question

我看到有类似的问题，但似乎没有解决我的问题。

我注册了一位新用户，但我获得了Warning: mysqli_query() expects parameter 1 to be mysqli, boolean given in C:\wamp\www\ticketing\newcustomer.php on line 11

我不知道错误是什么，因为我拥有正确的连接凭据，而且就我所知，SQL查询看起来很好。

<?php
session_start();
$con = mysqli_connect("localhost", "root", "", "ticketing");
$username = $_POST['username'];
$password = $_POST['pass'];
$fullname = $_POST['fullname'];

$query = mysqli_query($con,"INSERT INTO customer (username, password, fullname)
        VALUES ($username, $password, $fullname)"); 

if (!mysqli_query($query,$con)){
    die ("An error in the SQL Query: " . mysqli_error());
}

?>

Answer 1

你的变量被错误地注入，用一个＆＃39;来封装它们。像这样

$query = mysqli_query($con,"INSERT INTO customer (username, password, fullname)
    VALUES ('$username', '$password', '$fullname')"); 

重要！首先像这样逃避变量

$username = mysqli_real_escape_string($con , $username);
$password = mysqli_real_escape_string($con , $password);
$fullname = mysqli_real_escape_string($con , $fullname);