Registration system with php and mysql

Question

im new to php and mysql (using wamp)

im getting the following error when i run my script, any idea what to fix?

Warning: mysqli_select_db() expects parameter 1 to be mysqli, string given in C:\wamp64\www\web1\Register.php on line 79

Warning: mysqli_query() expects parameter 1 to be mysqli, string given in C:\wamp64\www\web1\Register.php on line 81

line 79 t0 83

 79   mysqli_select_db($database_localhost, $localhost);
 80   $query_Register = "SELECT * FROM mytable";
 81   $Register = mysqli_query($query_Register, $localhost) or die(mysql_error());
 82   $row_Register = mysql_fetch_assoc($Register);
 83   $totalRows_Register = mysql_num_rows($Register);

Here is the database connection:

<?php
# FileName="Connection_php_mysqli.htm"
# Type="mysqli"
# HTTP="true"
$hostname_localhost = "localhost";
$database_localhost = "mydatabase";
$username_localhost = "root";
$password_localhost = "";
$localhost = mysqli_connect($hostname_localhost, $username_localhost, $password_localhost) or trigger_error(mysql_error(),E_USER_ERROR); 
?>

Answer 1

i have changed the position of the connection link and database name from

    mysqli_select_db($database_localhost, $localhost);

to

    mysqli_select_db($localhost, $database_localhost);

the first error disappeared, but the second error still persist

forgot to mention that (html code) registration form is not showing

Answer 2

As Andrew noted in the comment, the mysql extension was deprecated in PHP 5.5.0 and removed in PHP 7.0.0. You should be using mysqli.

Nonetheless mysql expects the second parameter to be a database resource. You create a resource like this:

$dbResource = mysql_connect('localhost', 'mysql_user', 'mysql_password');

then you would select the database with something like

mysql_select_db('your_database_name', $dbResource);