致命错误:在非对象中调用成员函数query() | 在非对象中调用成员函数query

本文介绍了致命错误:在非对象中调用成员函数query()的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

致命错误:在线上的非对象上调用成员函数query():$ result = $ conn-> query($ sql)或die(mysqli_error());

Fatal error: Call to a member function query() on a non-object on line:$result = $conn->query($sql) or die(mysqli_error());

谁知道哪里出了问题以及如何解决?

Who knows whats wrong and how to fix it?

<?php
function dbConnect($usertype, $connectionType = 'mysqli') {
  $host = 'localhost';
  $db = 'phpsols';
  if ($usertype  == 'read') {
    $user = 'psread';
    $pwd = '123';
  } elseif ($usertype == 'write') {
    $user = 'pswrite';
    $pwd = '123';
  } else {
    exit('Unrecognized connection type');
  }
  if ($connectionType == 'mysqli') {
    return new mysqli($host, $user, $pwd, $db) or die ('Cannot open database');
  } else {
    try {
      return new PDO("mysql:host=$host;dbname=$db", $user, $pwd);
    } catch (PDOException $e) {
      echo 'Cannot connect to database';
      exit;
    }
  }
}

// connect to MySQL
$conn = dbConnect('read');
// prepare the SQL query
$sql = 'SELECT * FROM images';
// submit the query and capture the result
**$result = $conn->query($sql) or die(mysqli_error());**
// find out how many records were retrieved
$numRows = $result->num_rows;
?>
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Connecting with MySQLi</title>
</head>

<body>
<p>A total of <?php echo $numRows; ?> records were found.</p>
</body>
</html>

推荐答案

罪魁祸首最可能是这行:

The culprit is most likely this line:

return new mysqli($host, $user, $pwd, $db) or die ('Cannot open database');

do xyz or die()构造与return语句结合使用会导致有趣的行为(即整个事物都被解释为OR表达式，并且由于new mysqli永远不会为假，因此永远不会处理"die".) .请参见此处.

The do xyz or die() construct leads to funny behaviour in conjuction with the return statement (i.e. the whole thing is interpreted as an OR expression and because new mysqli will never be false, the "die" is never processed.). See a similar case here.

相反，请执行以下操作:

Do this instead:

$result = new mysqli($host, $user, $pwd, $db) ;
if (!$result) die (....);
return $result;

此外，我认为您永远也不会遇到PDO连接错误，因为:

Also, slightly related, I think you will never catch a PDO connection error because this:

return new PDO("mysql:host=$host;dbname=$db", $user, $pwd);

将总是退出该功能，并且永远不会到达catch块.与您的实际问题一样，解决方案是先将对象传递给$result变量.

will always exit the function, and never reach the catch block. As with your actual problem, the solution is to pass the object to a $result variable first.

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