How can user authentication be implemented in PHP to allow users to add comments to images?

User authentication can be implemented in PHP by requiring users to log in with their credentials before allowing them to add comments to images. This can be achieved by creating a login form that validates the user's input against a database of registered users. Once the user is authenticated, they can then submit comments that are associated with their account. 

<?php
session_start();

// Check if user is logged in
if(!isset($_SESSION['user_id'])) {
    header("Location: login.php");
    exit();
}

// Code to add comment to image goes here

?>

Keywords

PHP user authentication comments images security

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