How to fix 'mysqli_connect(): (hy000/1045): access denied' error?

This error indicates that the provided credentials for the MySQL database are incorrect. Example:

mysqli_connect('localhost', 'wrong_user', 'wrong_pass', 'database_name');

Solution:

// Provide the correct credentials
mysqli_connect('localhost', 'correct_user', 'correct_pass', 'database_name');

Always double-check your database credentials.