Mysqli_Select_Db() Expects Parameter 1 to Be MySQLi, String Given

mysqli_select_db() expects parameter 1 to be mysqli, string given

Your arguments are in the wrong order. The connection comes first according to the docs

<?php
require("constants.php");

// 1. Create a database connection
$connection = mysqli_connect(DB_SERVER,DB_USER,DB_PASS);

if (!$connection) {
    error_log("Failed to connect to MySQL: " . mysqli_error($connection));
    die('Internal server error');
}

// 2. Select a database to use 
$db_select = mysqli_select_db($connection, DB_NAME);
if (!$db_select) {
    error_log("Database selection failed: " . mysqli_error($connection));
    die('Internal server error');
}

?>

Warning: mysqli_select_db() expects parameter 1 to be mysqli, null given

Complete Guide

Note :

With mysqli you can specify the Database Name in mysqli_connect()

You have to use mysqli_connect_error(), not mysqli_error(), to get the
error from mysqli_connect(), because the latter requires you to supply
a valid connection.

<?php

    // Creating a database connection

    $connection = mysqli_connect("localhost", "root", "", "databse_name");
    if (!$connection) {
        die("Database connection failed: " . mysqli_connect_error());
    }

    // Selecting a database 

    $db_select = mysqli_select_db($connection, "databse_name");
    if (!$db_select) {
        die("Database selection failed: " . mysqli_connect_error());
    }

?>

Just do copy and paste & Then change the database name

mysqli_select_db() expects parameter 1 to be mysqli, string given & mysqli_error() expects exactly 1 parameter, 0 given in DATABASE_CONNECT_ERROR

First of all you no need to have "" for your DB connection because you pass it as a variable

Second thing is In MYSQLI always Pass $connection with your Connection.

And for a mysqli_error pass $connection to let server know you are looking for error in Database Connection.

Try this.

$connect = mysqli_connect($db_server, $db_user, $db_password)
    or die( DATABASE_CONNECT_ERROR . mysqli_error($connect) );
mysqli_select_db($connect, $db_database)
    or die( DATABASE_CONNECT_ERROR . mysqli_error($connect) );

Edit

either way you can try connect your DB As follow

$connect = mysqli_connect($db_server, $db_user, $db_password, $db_database);

// If no connection than Print error
if (mysqli_connect_errno())
  {
      echo "No Active DB Connection Please check: " . mysqli_connect_error();
  }

Warning: mysqli_select_db() expects parameter 1 to be mysqli

Try This below code:

You have to pass first $conn when select the DB, you have changed the parameter order.

<?php

 // this will avoid mysql_connect() deprecation error.
 error_reporting( ~E_DEPRECATED & ~E_NOTICE );
 // but I strongly suggest you to use PDO or MySQLi.

define('DBHOST', 'localhost');
define('DBUSER', 'root');
define('DBPASS', '');
define('DBNAME', 'simple_login');

$conn = mysqli_connect(DBHOST,DBUSER,DBPASS);
$dbcon = mysqli_select_db($conn,DBNAME);

if ( !$conn ) {
 die("Connection failed : " . mysqli_connect_errno());
 }

if ( !$dbcon ) {
 die("Database Connection failed : " . mysqli_connect_errno());
 }

Hope this help!!

HtmlEncode UTF-8

Update (Solved): Adding <%@CODEPAGE=65001%> at the start of the page corrected the problem (http://technet.microsoft.com/en-us/library/bb742422.aspx)

Many thanks for all of the suggestions.