PHP Convert mysql to mysqli [duplicate] - php

Question

This question already has answers here:
Can I mix MySQL APIs in PHP?
(4 answers)
Closed 3 years ago.
The following script works fine:
$host="localhost"; // Host name
$username=""; // Mysql username
$password=""; // Mysql password
$db_name="test"; // Database name
$tbl_name="members"; // Table name
// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
// username and password sent from form
$myusername=$_POST['myusername'];
$mypassword=$_POST['mypassword'];
// To protect MySQL injection (more detail about MySQL injection)
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);
$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result=mysql_query($sql);
// Mysql_num_row is counting table row
$count=mysql_num_rows($result);
// If result matched $myusername and $mypassword, table row must be 1 row
if($count==1){
// Register $myusername, $mypassword and redirect to file "login_success.php"
session_register("myusername");
session_register("mypassword");
header("location:login_success.php");
}
else {
echo "Wrong Username or Password";
}
Why, when I replace only the mysql_connect and mysql_select_db statements (keeping everything else including all passwords the same) with the following, do i get the "Wrong Username or Password" echo?
mysqli_connect($host,$username,$password,$db_name) or die("cannot connect");

Answer 1

It is because the MySQL and MySQLi database connections are not linked. When you make a connection to database with MySQLi, you have to use that connectio.
Example:
$mysqli = new mysqli('localhost', 'user', 'password', 'database');
$result = $mysqli->query("SELECT * FROM users");