致命错误 在 null 上调用成员函数 prepare()

问题描述

我正在尝试检查电子邮件是否已在注册中使用.我在学校做的时候还不错，现在突然报错:

I am trying to check if email was already used in Registration. It worked well when I was working on it in the school but now it suddenly shows an error:

致命错误:在 null 上调用成员函数 prepare()

Fatal error: Call to a member function prepare() on null

我用它来包含

define("dbserver", "localhost");
define("dbuser", "user");
define("dbpass", "");
define("dbname", "user");    


$db = new PDO(
"mysql:host=" .dbserver. ";dbname=" .dbname,dbuser,
array(
PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8",
PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8"
) );

在这里

session_start();
include "DBjoin.php";
if(isset($_POST["email"])) {
  $_SESSION['email'] = $_POST["email"];
  }   
if(isset($_POST["nick"])) {
  $_SESSION['nick'] = $_POST["nick"];         
}    
if(isset($_POST["pass"])) {
  $_SESSION['pass'] = $_POST["pass"];
  $_SESSION['pass'] = base64_encode($_SESSION['pass']);    
}
$sthandler = $db->prepare("SELECT Email FROM Registrace WHERE Email =     :email");
$sthandler->bindParam(':email', $_SESSION['email']);
$sthandler->execute();               
if(filter_var($_SESSION['email'], FILTER_VALIDATE_EMAIL)) {
if($sthandler->rowCount() > 0){
      echo "Email is used";}

推荐答案

(我想通了).

我终于弄清楚为什么你的代码不起作用，我原来的答案不再适用，我已经解决了.

I finally figured out why your code is not working and my original answer no longer applies, which I have stricken out.

您的连接不起作用的原因是因为您从连接参数中遗漏了 dbpass 常量.

The reason why your connection does not work, is because you left out the dbpass constant from the connection parameter.

$db = new PDO(
"mysql:host=" .dbserver. ";dbname=" .dbname,dbuser,dbpass,
array(
PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8",
PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8"
) );

• 即使您可能没有为其设置密码，它仍然需要成为参数的一部分.

  • Even though you may not have a password set for it, it is still required to be part of the parameters.

    http://php.net/manual/en/ref.pdo-mysql.connection.php

    原始答案，不再适用.(见上面的编辑).

    Original answer, which no longer applies. (see edit above).

    <打击>TBH，经过一番努力，我还是无法重现该错误.

    TBH, I wasn't able to reproduce the error, amidst a great effort.

    然而；对此进行修补后，发现 PDO(至少，我服务器上的那个)不允许 constants 用作 DSN 中的前 2 个参数.

    However; after tinkering with this, have discovered that PDO (least, the one on my server), won't allow for constants be used as the first 2 parameters in the DSN.

    旁注:如果您所说的在您的学校有效，那么可能使用了我不知道的设置.

    Sidenote: If what you say worked at your school, then there may be a setting used that I don't know about.

    但是，您可以将变量分配给常量，然后在 DSN 中使用这些变量.

    You can however, assign variables to the constants, then use those variables in the DSN.

    $servername = "localhost";
    $dbname = "user";
    
    define("dbuser", "user");
    define("dbpass", "");
    
    $dsn = "mysql:host=$servername;dbname=$dbname";
    
    $username = dbuser; // variable equals constant
    $password = dbpass; // variable equals constant
    
    $options = array(
    PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8",
    PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8"
    ); 
    
    $db = new PDO($dsn, $username, $password, $options);
    

    有关 PDO 连接的更多信息，请访问:

    For more information on PDO connection, visit:

    • http://php.net/manual/en/ref.pdo-mysql.connection.php

    将错误报告添加到将有助于查找错误的文件顶部.

    Add error reporting to the top of your file(s) which will help find errors.

    <?php 
    error_reporting(E_ALL);
    ini_set('display_errors', 1);
    
    // rest of your code
    

    旁注:错误报告只应在暂存阶段进行，切勿在生产中进行.

    Sidenote: Error reporting should only be done in staging, and never production.

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