PHP连接到mysql数据库

Question

I'm trying to make a connection between my database and the login form that I'm using in my website, but I'm facing a problem with that, so every time I click on login, this message appears "No database selected"

Here is my code:

<?php
session_start();

if(isset($_POST['Email']) && isset($_POST['Username']) && isset($_POST['Password']))
{
    $mysql_hostname = "localhost";
    $mysql_user = "root";
    $mysql_password = "";
    $mysql_database = "db_3300";

    $con=mysql_connect($mysql_hostname, $mysql_user, $mysql_password, $mysql_database);

    // Check connection
    if (!$con)
    {
        die('Could not connect: ' . mysql_error());
    }

    $result = mysql_query("SELECT * FROM users where
    Username='".$_POST['Username']."'
    AND Email ='".$_POST['Email']."'
    AND Password ='".$_POST['Password']."'")
    or die (mysql_error());


    while($row = mysql_fetch_array($result))
    { echo $result; 
        echo "You are successfully connected";
        $_SESSION["authenticated"] = true;
        exit;
    }

    mysql_close($con);
}
?>

I hope that someone could help me with this.

Answer 1

You haven't selected your database yet.

Do this after your $con

$con=mysql_connect($mysql_hostname, $mysql_user, $mysql_password); //Removed the $mysql_database from here
$db_selected = mysql_select_db($mysql_database, $con); //Added this

^{Also, You are using mysql_* functions which will be deprecated in the coming versions of PHP. Switch to mysqli_* or PDO Instead.}

Answer 2

Switch over to mysqli while you can. It is really easy, in fact your code is styled for it too.

$con = mysqli_connect($mysql_hostname, $mysql_user, $mysql_password, $mysql_database);

Now, whenever you do a mysqli_query, you just do

$query = mysqli_query($con, "SELECT * FROM users WHERE...");

so you have to include the connection in the mysqli_query