ethics-canvas/canvas/php/load_shared_canvases.php

<?php
    /* Retrieves all the canvases created by the user passed by parameter in JSON format */
    
    // Retrieve user credentials
    $email = $_POST['loggedin_user_email'];
    
    require_once('../../php/db_utils.php');
    $conn = db_connect(); // Connect to the database
    
    // Check if the username already exists
    if(!($result = mysqli_query($conn, 'SELECT name FROM user WHERE username = "' . $email . '";'))) {
        echo 400; // Wrong query
    }
    else if(mysqli_num_rows($result) != 1) { // User not registered or duplicated
        echo 401;
    }
    else { // User registered: Retrieve canvases
        if(!($result = mysqli_query($conn,
                                    'SELECT * FROM canvas INNER JOIN collaborators ON canvas.canvas_id = collaborators.canvas_id WHERE collaborators.collaborator = "' . $email . '" AND NOT canvas.user_id = "' . $email . '" ORDER BY canvas_name;'))) {
            echo 400; // Wrong query
        }
        else { // Request accepted
            $rows = array();
            while($r = mysqli_fetch_assoc($result)) {
                $rows[] = $r;
            }
            echo json_encode($rows);
        }
    }
    mysqli_free_result($result);
    db_close($conn); // Close the database
?>