Question

<?php
require_once'config.php';
if(isset($_POST['subscribe'])){
  $email=$_POST['email'];

  //check the email if it is already subscribed or not
  if(strlen($email)>3){             
    $stmt=$mysql->prepare("SELECT * FROM subscribers WHERE email=?");
    $stmt->bind_param('s', $email);
    $stmt->execute();
    if($stmt->field_count > 0){ // if not then add
      unset($mysql); unset($stmt);
      $mysql=new mysqli(HOST,USER,PASS,DB);     
      $stmt=$mysql->prepare('INSERT INTO subscribers(email) VALUES (?)');
      $stmt->bind_param('s', $email);
      $stmt->execute();
      if($stmt->affected_rows>0){
        echo "subscribed";
      }
    } else { //else is there
      echo "Already there";
    }
  } else echo "empty string";
}
?>

如果我删除了行unset($mysql); unset($stmt);，则会导致致命错误：Bind_param Non-Object Error。但如果我取消设置然后重新定义对象然后工作正常。任何人都可以解释原因吗？

Answer 1

警告：这是未经测试的。但是，我认为如何以更清洁的方式编写这一点非常重要。特别是，将你的意图分解为特定的函数，每个函数都做一件事并返回结果。这将有助于防止代码混乱，并且可以更轻松地自行测试每个块。

require_once'config.php';

//It is always good to declare stuff like this in a central place
//That way they're easy to change, and you change it everywhere you have that express intent
$SQL_FIND_SUBSCRIPTION = "SELECT * FROM subscribers WHERE email=?";
$SQL_NEW_SUBSCRIPTION = "INSERT INTO subscribers(email) VALUES (?)";

//Functions make testing easy!
static function attemptSubscription($postValues, &$returnMsg) {
  if (   isset($postValues['subscribe']) 
      && isset($postValues['email']) //be sure to validate both!

  {
    if (isValidEmail($postValues['email'])) {
      subscribe($email);//this syntax may be off.

    } else {
      $returnMsg = "A valid email address must be provided.";
      return false;
    }
  } else {
    $returnMsg = "No subscription was attempted.";
    return false;
  }
}


//Returns true if the passed parameter is a valid email
static function isValidEmail($email) {
  //left as an exercise for the reader. 
}

//Assumes a valid email address is being passed
static function subscribe($email, &$returnMsg) {
  global $mysql; //sadly, this is the cleanest way possible without using a class.
  $stmt=$mysql->prepare($SQL_FIND_SUBSCRIPTION);
  $stmt->bind_param('s', $email);
  $stmt->execute();
  $stmt->store_result(); // This lets you reuse stmt

  if($stmt->field_count > 0){ 
    //Subscription already exists
    $returnMsg = "This subscription already exists.";
    return true;
  } else { 
    //Subscription must be added
    return addNewSubscription($email, $returnMsg);
  }
}

static function addNewSubscription($email, &$returnMsg) {
  global $mysql; // :(
  $stmt=$mysql->prepare($SQL_NEW_SUBSCRIPTION);
  $stmt->bind_param('s', $email);
  $stmt->execute();
  $stmt->store_result();

  if($stmt->affected_rows>0){
    $returnMsg = "New subscription successful!";
    return true;
  } else {
    $returnMsg = "New subscription failed.";//you can add more info here if you want
    return false;
  }

  $stmt->close();
}

//now actually execute
$resultMsg = "";
if (attemptSubscription($_POST, $resultMsg)) {
  echo "Success! ".$resultMsg;
} else {
  echo "Oh no! Failure! ".$resultMsg;
}



// ?> Note that eliding this will help remove nasty hidden characters from the rendered html

查看store_result了解更多信息。

使用这种配置，您可以验证各个命令是否正常工作，而不依赖于首先执行它们嵌套的结构。特别是，验证第二个SQL查询至关重要：非绑定错误通常是因为无法找到列或表。但是，也就是说，意识到prepare()语句所做的是向服务器发送查询以检查语法;该查询永远不会被重新发送，而是在服务器中保持“加载”，直到您告诉它（使用另一个语句）去掉它。随后绑定参数时，该参数将发送到服务器并放入可用插槽（?）。然后，由于此模型，您可以多次有效地执行此查询。

请注意，如果服务器上的查询没有新参数的未绑定插槽，则尝试绑定它将失败。如果服务器上的查询试图引用不可用的变量（例如列名），则此步骤也将失败。

从您提供的详细信息中不清楚确切的问题是什么，但是如果您以更干净的方式编写代码，调试这些问题将变得更加容易：您的第二个SQL语句是不是很糟糕？是不是你没有从第一个语句中正确释放服务器资源？

Mysql bind_param（）错误

1 个答案: