Which MySQL function is used to establish a connection to the database in PHP?     Select one:a. mysql_db_connect()b.mysqli_connect()              c. mysql_connect()             d.connect_mysql()

The correct answer is b. mysqli_connect(). This function is used in PHP to establish a connection to a MySQL database. Here's a step-by-step guide on how to use it:

1. First, you need to have your database details ready. These include the database host (usually 'localhost'), the database username, the database password, and the database name.

2. Next, in your PHP script, you call the function mysqli_connect() and pass the database details as parameters. Here's an example:

$host = 'localhost';
$username = 'your_username';
$password = 'your_password';
$db_name = 'your_database_name';

$conn = mysqli_connect($host, $username, $password, $db_name);

3. The function mysqli_connect() will return a connection object if the connection is successful. You can then use this connection object to perform database operations.

4. If the connection is not successful, the function mysqli_connect() will return false and you can check the connection error using the function mysqli_connect_error(). Here's an example:

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

5. Remember to close the connection after you're done with your database operations using the function mysqli_close(). Here's an example:

mysqli_close($conn);

So, the correct answer to your question is b. mysqli_connect().