我遇到无法从 MySQL 数据库(通过 PHP)检索结果的问题。我在其他地方使用了相同的功能，而且效果很好。但是此时我不断收到“警告:mysqli_query():无法获取 mysqli”错误。问题的详细说明如下。 我在我的 PHP 中的其他地方使用了一个非常相似的函数(如下所示的 getAllCountries)，它工作得很好:

function getAllCountries()
{
    $result = db_query("SELECT countryid, name FROM country ORDER BY name ASC");

    echo "<select class=addresscountry name=country>";
    while($row = mysqli_fetch_array($result)) {
      echo '<option value="' . $row['countryid'] . '">' . $row['name'] . '</option>';
    }
    echo "</select>";

    mysqli_close(db_connect());
}

所以问题如下:

我有一个包含以下代码的 php 文件:

<?php
require 'includes/functions.php';

function getUserPicPath()
{
    $userid = $_SESSION['userid'];

    $result = db_query("SELECT picture FROM user WHERE userid='$userid'");

    while($row = mysqli_fetch_array($result)) {
        $picturepath = $row['picture'];
    }

    echo $picturepath;

    mysqli_close(db_connect());
}

我的 functions.php 文件包含以下行(以及其他不相关的函数):

require 'dbfunctions.php';

我的 dbfunctions.php 看起来像这样:

<?php
function db_connect()
{
    require ".db_password.php";

    static $connection;

    if(!isset($connection)) {
        $connection = mysqli_connect('localhost',$username,$password,$dbname);
    }

    if($connection === false) {
        return mysqli_connect_error(); 
    }

    return $connection;
}

function db_query($query) 
{
    $connection = db_connect();

    $result = mysqli_query($connection,$query);

    return $result;
}

在我的 PHP 文档中，我调用了以下函数:

if ($userid == -1)
    {
        showNotAuthorizedPage();
    } else {
        myAccountPage();
    }

并且 myAccountPage() 函数与 getUserPicPath() 函数在同一文件中声明，此 getUserPicPath() 函数调用如下:

<div id="tabs-2">
    <p><?php getUserPicPath(); ?></p>
  </div>

我在我的网页上使用选项卡 ( http://jqueryui.com/tabs/#default )，这就是我想调用它的地方。 出现以下错误的 myAccountPage() 函数:

Warning: mysqli_query(): Couldn't fetch mysqli in C:\Users\Dennis\Documents\My Dropbox\xxx\zzz\www\Project Files\includes\dbfunctions.php on line 29
Call Stack
#   Time    Memory  Function    Location
1   0.0000  256880  {main}( )   ..\myaccount.php:0
2   0.0010  283328  myAccountPage( )    ..\myaccount.php:181
3   0.0070  285368  getUserPicPath( )   ..\myaccount.php:121
4   0.0070  285528  db_query( ) ..\myaccount.php:11
5   0.0070  285624  mysqli_query ( )    ..\dbfunctions.php:29

( ! ) Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, null given in C:\Users\Dennis\Documents\My Dropbox\me&roxy\WE\final project\Project Files\myaccount.php on line 13
Call Stack
#   Time    Memory  Function    Location
1   0.0000  256880  {main}( )   ..\myaccount.php:0
2   0.0010  283328  myAccountPage( )    ..\myaccount.php:181
3   0.0070  285368  getUserPicPath( )   ..\myaccount.php:121
4   0.0080  285768  mysqli_fetch_array ( )  ..\myaccount.php:13

( ! ) Notice: Undefined variable: picturepath in C:\Users\Dennis\Documents\My Dropbox\me&roxy\WE\final project\Project Files\myaccount.php on line 17
Call Stack
#   Time    Memory  Function    Location
1   0.0000  256880  {main}( )   ..\myaccount.php:0
2   0.0010  283328  myAccountPage( )    ..\myaccount.php:181
3   0.0070  285368  getUserPicPath( )   ..\myaccount.php:121

( ! ) Warning: mysqli_close(): Couldn't fetch mysqli in C:\Users\Dennis\Documents\My Dropbox\me&roxy\WE\final project\Project Files\myaccount.php on line 19
Call Stack
#   Time    Memory  Function    Location
1   0.0000  256880  {main}( )   ..\myaccount.php:0
2   0.0010  283328  myAccountPage( )    ..\myaccount.php:181
3   0.0070  285368  getUserPicPath( )   ..\myaccount.php:121
4   0.0100  285864  mysqli_close ( )    ..\myaccount.php:19

最佳答案

我想是因为第一次关闭数据库连接的时候忘记做:

unset($connection);

然后当您再次尝试连接到数据库时，它会崩溃，因为它仍然设置为关闭连接。

关于php - 警告 : mysqli_query(): Couldn't fetch mysqli，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24973330/