PHP MySQLi mysqli_select_db() - Database Selection

mysqli_select_db()

The mysqli_select_db() function is used to change the default database for a specific connection. Once the database is selected, all subsequent queries will be executed against this database.

EXAMPLE

<?php
$server = "localhost";
$username = "root";
$password = "";
$database = "mysqli_database";

$connection = mysqli_connect($server, $username, $password, $database);

if (mysqli_connect_errno()) {
    echo "Connection failed: " . mysqli_connect_error();
    exit();
}

// Switch to a different database on the same server
// NOTE: The mysqli_select_db() function changes the default database 
// for all subsequent queries. From this line onwards, all SELECT 
// and INSERT will look for tables inside the "other_database" database.
mysqli_select_db($connection, "other_database");

// Check which database is now active using the built-in MySQL DATABASE() function
if ($result = mysqli_query($connection, "SELECT DATABASE()")) {
    $row = mysqli_fetch_row($result);
    echo "Currently selected database is: " . $row[0];
    mysqli_free_result($result);
}

mysqli_close($connection);
?>

RESULT

The result will be displayed here...

Practical use: Although the database is usually specified during the mysqli_connect() call, this function allows us to switch to another database on the same server during script execution without having to create a new connection.

Returns TRUE on a successful database change and FALSE on error.

Useful in scripts that manage multiple different databases simultaneously.

Helps keep the code clean, as there is no need for multiple server logins.