What are some common mistakes made when using mysqli functions in PHP?

One common mistake when using mysqli functions in PHP is not properly handling errors. It's important to check for errors after each mysqli function call to ensure the query was executed successfully. Another mistake is not sanitizing user input, which can leave your application vulnerable to SQL injection attacks. Additionally, failing to close the database connection can lead to resource leaks and potentially slow down your application.

// Example of handling errors and closing the database connection properly
$conn = mysqli_connect("localhost", "username", "password", "database");

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

// Perform query
$sql = "SELECT * FROM users";
$result = mysqli_query($conn, $sql);

if (!$result) {
    die("Error executing query: " . mysqli_error($conn));
}

// Process results

// Close connection
mysqli_close($conn);