PHP说“未选择数据库".即使使用mysqli_select_db() [英] PHP says "No Database selected" even after using mysqli_select_db()

问题描述

我正在编写一个简单的代码，以从数据库中名为Plasma的表中提取2个元素. 似乎连接状况良好，但由于未知原因，我无法选择任何数据库.

I am writing a simple code to fetch 2 elements from a table in my database called Plasma. It seems the connection is being made well but I am unable to select any database due to unknown reason.

代码:

<?php
$db  = "Plasma"; 
$dbH = "localhost";
$dbU = "plasma";
$dbP = "plasma";
      $dbCon = mysqli_connect($dbH,$dbU,$dbP,$db);
        if(!dbCon){
            echo "Conenction Fail";
        }
        mysqli_select_db($dbCon,$db);
        $qry = "select Mid,Mname from ya_movies order by DOA limit 5;";
        $Response = mysqli_query($dbCon,$qry);
        echo mysqli_error($dbCon);                     ?>

输出为

No database selected

推荐答案

这是调试信息不​​足的典型情况:

It's a typical case of not enough debug information:

mysqli_select_db($dbCon, $db);

您无需检查返回值；它可能返回false表示它无法更改数据库(可能是由于权限).我建议将其放置并运行:

You don't check for the return value; it may return false to indicate it couldn't change the database (probably due to permissions). I would suggest putting this in place and run it:

if (!mysqli_select_db($dbCon, $db)) {
    die("Uh oh, couldn't select database $db");
}

如果发生这种情况，请仔细检查名称，权限等.

If this happens, double check the name, permissions, etc.

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