The mysqli_connect() function in PHP is used to open a new connection to a MySQL database server. It is part of the MySQLi (MySQL Improved) extension and supports both procedural and object-oriented programming.

🔧 Syntax

mysqli_connect(host, username, password, dbname, port, socket);

✅ Parameters

🧪 Basic Example

<?php
$conn = mysqli_connect("localhost", "root", "", "test_db");

if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>

🧰 With Port and Database

<?php
$conn = mysqli_connect("localhost", "root", "mypassword", "my_database", 3306);

if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected to database with port!";
?>

❌ Handling Connection Error

<?php
$conn = mysqli_connect("localhost", "wrong_user", "wrong_pass");

if (mysqli_connect_errno()) {
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
    exit();
}
?>

🧼 Closing the Connection

<?php
$conn = mysqli_connect("localhost", "root", "", "test_db");
if ($conn) {
    // Do something with the connection
    mysqli_close($conn); // Close connection
}
?>

📝 Notes:

• It’s best practice to check for errors after trying to connect.
• Use prepared statements with mysqli or switch to PDO for more secure and flexible database interactions.