What are some common methods for implementing user authentication in PHP, such as using sessions or reading from a file?

Implementing user authentication in PHP can be achieved using various methods such as sessions, reading from a file, or using a database to store user credentials. Sessions are commonly used as they provide a secure way to authenticate users by storing user information on the server. Reading from a file is another option where user credentials are stored in a text file and checked against when a user tries to log in. 

// Using sessions for user authentication
session_start();

// Check if user is logged in
if(isset($_SESSION['user_id'])) {
    // User is authenticated
    echo "User is authenticated.";
} else {
    // Redirect user to login page
    header("Location: login.php");
    exit();
}

Keywords

user authentication PHP sessions file reading implementation

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