select database using mysqli in config.php file - php

Question

I have a nice free for searching a database. It was written with PHP and MySql...however for whatever reason, I occasionally need to add an "i" at the end of MySql occasionally to get things working. I can connect and login, but not select the database, since it passes through until I get the
"request "Unable to select database."
Here's the meat from the config.php file that probably has the issue :
$SETTINGS["hostname"]='localhost';
$SETTINGS["mysql_user"]='root';
$SETTINGS["mysql_pass"]='root';
$SETTINGS["mysql_database"]='myDB';
$SETTINGS["data_table"]='data'; // this is the default database name that we used
/* Connect to MySQL */
if (!isset($install) or $install != '1') {
$connection = mysqli_connect($SETTINGS["hostname"], $SETTINGS["mysql_user"], $SETTINGS["mysql_pass"]) or die ('Unable to connect to MySQL server.<br ><br >Please make sure your MySQL login details are correct.');
$db = mysqli_select_db($SETTINGS["mysql_database"], $connection) or die ('request "Unable to select database."');
};
?>

Answer 1

The problem you are facing is the line in which you select the database;
$db = mysqli_select_db($SETTINGS["mysql_database"], $connection) or die ('request "Unable to select database."');
As defined by the documentation of mysqli_select_db() the connection $connection ($link in the docs) should be the first argument:
$db = mysqli_select_db($connection, $SETTINGS["mysql_database"]);
The reason why you need to occasionally add an i to every mysql_* function is because all mysql_* functions are officially deprecated, no longer maintained and removed in PHP 7.0.0. You should update your code with PDO or MySQLi to ensure the functionality of your project in the future.

Answer 2

With mysqli, you can select your database directly using the connection method :
$connection = mysqli_connect($SETTINGS["hostname"], $SETTINGS["mysql_user"], $SETTINGS["mysql_pass"], $SETTINGS["mysql_database"]);
If you want to use mysqli_select_db, you need to reverse your arguments. First the connection, then the database :
mysqli_select_db($connection, $SETTINGS["mysql_database"]);