代码没问题，为什么是失败呢 " 失败当前用户插入的ID为0"

Question

<?php

if (trim($_POST['password']) != trim($_POST['repassword'])) {

   exit('两次密码不一致,请返回上一页');

}

$username = trim($_POST['username']);

$password = md5(trim($_POST['password']));

$time = time();

$ip = $_SERVER['REMOTE_ADDR'];

$conn = mysqli_connect('localhost', 'root', 'root');

//如果有错误，存在错误号
if (mysqli_errno($conn)) {

   echo mysqli_error($conn);

   exit;
}

mysqli_select_db($conn, 'text');

mysqli_set_charset($conn, 'utf8');

$sql = "insert into user(username,password,createtime,createip) values('" . $username . "','" . $password . "','" . $time . "','" . $ip . "')";

$result = mysqli_query($conn, $sql);

if ($result) {
   echo '成功';
} else {
   echo '失败';

}

echo '当前用户插入的ID为' . mysqli_insert_id($conn);

mysqli_close($conn);

?>

Answer 1

看看数据库里面是不是已经有了那条记录了，不能重复的

Answer 2

1. sql语句是否与数据库字段对应

2. sql语句里面的字段问题
   

$sql = "insert into user(`username`,`password`,`createtime`,`createip`) values ('" . $username . "','" . $password . "','" . $time . "','" . $ip . "')";