In PHP, the mysqli_connect() function is used to establish a connection to a MySQL database using the MySQLi extension in a procedural style. Here's a breakdown of how it works:

Syntax

  mysqli_connect('localhost', 'username', 'password', 'database');

Parameters

1. host: The hostname of the MySQL server. For a local server, you can use 'localhost'. If you're connecting to a remote server, use the IP address or domain name of that server.

2. username: The MySQL username you want to connect with. This user must have the appropriate permissions to access the specified database.

3. password: The password associated with the MySQL username.

4. database: The name of the database you want to select after connecting. This parameter is optional; if not provided, you need to select the database using mysqli_select_db() later.

5. port: The port number to use for the connection. The default MySQL port is 3306. This parameter is optional.

6. socket: The socket or named pipe to use for the connection. This parameter is optional.

Example

// Connect to the database
$conn = mysqli_connect('localhost', 'username', 'password', 'database');

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

echo "Connected successfully";

Error Handling

If the connection fails, mysqli_connect() returns false. You can use mysqli_connect_error() to retrieve a string description of the last connection error.

Closing the Connection

It's a good practice to close the connection once you're done with it using mysqli_close():

mysqli_close($conn);

Notes

• MySQLi (MySQL Improved) is an extension that provides an improved interface for accessing MySQL databases compared to the old mysql extension.
• Procedural vs. Object-Oriented: MySQLi can be used in both procedural and object-oriented styles. The example provided uses the procedural style.