PHP消息"Error: No database selected"，关注此脚本

Question

我有这个脚本，但我不知道当我点击主页上的"发布"按钮时这里可能出了什么问题。错误可能来自哪里？

页面脚本：

<?php 
session_start();
    include("dbconnection.php");
 function clean($str) {
        $str = @trim($str);
        if(get_magic_quotes_gpc()) {
            $str = stripslashes($str);
        }
        return mysql_real_escape_string($str);
    }
$messages = clean($_POST['message']);
$user =clean($_POST['name']);
$pic =clean($_POST['name1']);
$poster =clean($_POST['poster']);
$sql="INSERT INTO message (messages, user, picture, date_created, poster)
VALUES
('$messages','$user','$pic','".strtotime(date("Y-m-d H:i:s"))."','$poster')";
mysql_query("UPDATE messages SET picture = '$pic' WHERE FirstName='$user'");
if (!mysql_query($sql,$con))
  {
  die('Error: ' . mysql_error());
  }
header("location: lol.php");
exit();
$name=$_POST['name'];
$pic=$_POST['name1'];
mysql_query("UPDATE messages SET picture = '$pic' WHERE FirstName='$name'");
?> 

这是数据库连接文件：

$con = mysql_connect("hostname","username","pass");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }
mysql_select_db("asl", $con);
?>

Answer 1

确保已使用 mysql_select_db 选择了数据库

mysql_connect('hostname','username','password') or die("not able to connect");
mysql_select_db('myDatabase');

并且mysql_扩展已被弃用。不要使用它

Answer 2

此错误似乎是由选择wrong database或not selecting it.引起的

检查dbconnection.php以及其中的这一行

mysql_select_db("your_database_name",$your_connection);

查看此行是否存在并指向数据库，并确保此数据库存在

更新似乎您的文件未包含在内，请尝试require()，以便产生致命错误，您可以看到文件是否包含

 require("dbconnection.php"); // will produce fatal errors 

Answer 3

首先mysql_connect已经过时且不安全，最好使用 PDO

    <?php 
    session_start();
    include("dbconnection.php");
    function clean($str) {
            $str = @trim($str);
            if(get_magic_quotes_gpc()) {
                        $str = stripslashes($str);
            }
            return mysql_real_escape_string($str);
        }
    $messages = clean($_POST['message']);
    $user =clean($_POST['name']);
    $pic =clean($_POST['name1']);
    $poster =clean($_POST['poster']);
    $sql = $db->prepare("INSERT INTO message (messages, user, picture, date_created, poster) VALUES (:messages, :user, :picture, :date_created, :poster)");
    $sql->bindParam(':messages', $messages);
    $sql->bindParam(':user', $user);
    $sql->bindParam(':picture', $pic);
    $sql->bindParam(':date_created', strtotime(date("Y-m-d H:i:s")));
    $sql->bindParam(':poster', $poster);
    $stmt = $db->prepare("UPDATE messages SET picture = :picture WHERE FirstName = :user");
    $stmt->bindParam(':picture', $pic);
    $stmt->bindParam(':user', $user);
    $stmt->execute();

    if (!$sql->execute())
    {
            die('Error: ' . mysql_error());
    }

    $name=$_POST['name'];
    $pic=$_POST['name1'];
    $stmt_2 = $db->prepare("UPDATE messages SET picture = :picture WHERE FirstName = :name");
    $stmt_2->bindParam(':picture', $pic);
    $stmt_2->bindParam(':name', $name);
    $stmt_2->execute();
    header("location: lol.php");
    ?> 

这是数据库连接文件：

    <?php
            //Connect to sql db
            try {
                    $user_db = "username";
                    $pass_db = "password";
                    $db = new PDO('mysql:host=localhost;dbname=asl', $user_db, $pass_db);
            } catch (PDOException $e) {
                    print "Error!: " . $e->getMessage() . "<br/>";
                    die();
            }
    ?>