10_users.php

<?php
// Chapter-10: Exercises

// Question-1 

// 1. Make a web page that uses a cookie to keep track of how many times a user has viewed the page. 
// The first time a particular user looks at the page, it should print something like “Number of views: 1.” 
// The second time the user looks at the page, it should print “Number of views: 2,” and so on.

// Answer-1
$view_count = 1 + ($_COOKIE['view_count'] ?? 0);
setcookie('view_count', $view_count);
print "<p>Hi! Number of times you've viewed this page: $view_count.</p>";

// Question-2

// 2. Modify the web page from the first exercise so that it prints out a special message on the 5th, 10th, 
// and 15th times the user looks at the page. Also modify it so that on the 20th time the user looks at the page, 
// it deletes the cookie and the page count starts over.

// Answer-2

$view_count = 1 + ($_COOKIE['view_count'] ?? 0);
if ($view_count == 20) {
    // An empty value for setcookie() removes the cookie
    setcookie(
        'view_count',
        ''
    );
    $msg = "<p>Time to start over.</p>";
} else {
    setcookie('view_count', $view_count);
    $msg = "<p>Hi! Number of times you've viewed this page: $view_count.</p>";
    if ($view_count == 5) {
        $msg .= "<p>This is your fifth visit.</p>";
    } elseif ($view_count == 10) {
        $msg .= "<p>This is your tenth visit. You must like this page.</p>";
    } elseif ($view_count == 15) {
        $msg .= "<p>This is your fifteenth visit. " .
            "Don't you have anything else to do?</p>";
    }
}
print $msg;

// Question-3

// 3. Write a PHP program that displays a form for a user to pick his favorite color from a list of colors. 
// Make another page whose background color is set to the color that the user picks in the form. 
// Store the color value in $_SESSION so that both pages can access it.

// Answer-3

// The color-picking page:
// Start sessions first thing so we can use $_SESSION freely later
session_start();
// Load the form helper class
require 'FormHelper.php';
$colors = array(
    'ff0000' => 'Red',
    'ffa500' => 'Orange',
    'ffffff' => 'Yellow',
    '008000' => 'Green',
    '0000ff' => 'Blue',
    '4b0082' => 'Indigo',
    '663399' => 'Rebecca Purple'
);
// The main page logic:
// - If the form is submitted, validate and then process or redisplay
// - If it's not submitted, display
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    // If validate_form() returns errors, pass them to show_form()
    list($errors, $input) = validate_form();
    if ($errors) {
        show_form($errors);
    } else {
        // The submitted data is valid, so process it
        process_form($input);
    }
} else {
    // The form wasn't submitted, so display
    show_form();
}
function show_form($errors = array())
{
    global $colors;
    // Set up the $form object with proper defaults
    $form = new FormHelper();
    // All the HTML and form display is in a separate file for clarity
    include 'color-form.php';
}
function validate_form()
{
    $input = array();
    $errors = array();
    // color must be a valid color
    $input['color'] = $_POST['color'] ?? '';
    if (!array_key_exists($input['color'], $GLOBALS['colors'])) {
        $errors[] = 'Please select a valid color.';
    }
    return array($errors, $input);
}

function process_form($input)
{
    global $colors;
    $_SESSION['background_color'] = $input['color'];
    print '<p>Your color has been set.</p>';
}

// The code relies on the FormHelper.php file discussed in Chapter 7. 
// The color-form.php file referenced, which displays the form HTML, contains: ?>
<form method="POST" action="<?= $form->encode($_SERVER['PHP_SELF']) ?>">
    <table>
        <?php if ($errors) { ?>
            <tr>
                <td>You need to correct the following errors:</td>
                <td>
                    <ul>
                        <?php foreach ($errors as $error) { ?>
                            <li><?= $form->encode($error) ?></li>
                        <?php } ?>
                    </ul>
                </td>
            <?php } ?>
        <tr>
            <td>Favorite Color:</td>
            <td><?= $form->select($colors, ['name' => 'color']) ?></td>
        </tr>
        <tr>
            <td colspan="2" align="center">
                <?= $form->input('submit', [
                    'name' => 'set',
                    'value' => 'Set Color'
                ]) ?>
            </td>
        </tr>
    </table>
    <?php

    // The page with background color set:
    
    // Start sessions first thing so we can use $_SESSION freely later
    session_start();
    ?>
    <html>

    <head>
        <title>Background Color Example</title>

    <body style="background-color:<?= $_SESSION['background_color'] ?>">
        <p>What color did you pick?</p>
    </body>

    </html><?php


    // Question-4
    
    // 4. Write a PHP program that displays an order form. The order form should list six products.
    // Next to each product name there should be a text box into which a user can enter how many of 
    // that product she wants to order.
    // When the form is submitted, the submitted form data should be saved into the session.
    // Make another page that displays the contents of the saved order, a link back to the order form page,
    // and a Check Out button. If the link back to the order form page is clicked, the order form page should be
    // displayed with the saved order quantities from the session in the text boxes.
    // When the Check Out button is clicked, the order should be cleared from the session.
    
    // Answer-4
    
    // The ordering page:
    session_start();
    // This assumes FormHelper.php is in the same directory as this file.
    require 'FormHelper.php';
    // Set up the array of choices in the select menu.
// This is needed in display_form(), validate_form(),
// and process_form(), so it is declared in the global scope.
    $products = [
        'cuke' => 'Braised Sea Cucumber',
        'stomach' => "Sauteed Pig's Stomach",
        'tripe' => 'Sauteed Tripe with Wine Sauce',
        'taro' => 'Stewed Pork with Taro',
        'giblets' => 'Baked Giblets with Salt',
        'abalone' => 'Abalone with Marrow and Duck Feet'
    ];
    // The main page logic:
// - If the form is submitted, validate and then process or redisplay
// - If it's not submitted, display
    if ($_SERVER['REQUEST_METHOD'] == 'POST') {
        // If validate_form() returns errors, pass them to show_form()
        list($errors, $input) = validate_form2();
        if ($errors) {
            show_form($errors);
        } else {
            // The submitted data is valid, so process it
            process_form2($input);
        }
    } else {
        // The form wasn't submitted, so display
        show_form2();
    }

    function show_form2($errors = array())
    {
        global $products;
        $defaults = array();
        // Start out with 0 as a default
        foreach ($products as $code => $label) {
            $defaults["quantity_$code"] = 0;
        }
        // If quantities are in the session, use those
        if (isset($_SESSION['quantities'])) {
            foreach ($_SESSION['quantities'] as $field => $quantity) {
                $defaults[$field] = $quantity;
            }
        }
        $form = new FormHelper($defaults);
        // All the HTML and form display is in a separate file for clarity
        include 'order-form.php';
    }

    function validate_form2()
    {
        global $products;
        $input = array();
        $errors = array();
        // For each quantity box, make sure the value is
// a valid integer >= 0
        foreach ($products as $code => $name) {
            $field = "quantity_$code";
            $input[$field] = filter_input(
                INPUT_POST,
                $field,
                FILTER_VALIDATE_INT,
                ['options' => ['min_range' => 0]]
            );
            if (is_null($input[$field]) || ($input[$field] === false)) {
                $errors[] = "Please enter a valid quantity for $name.";
            }
        }
        return array($errors, $input);
    }

    function process_form2($input)
    {
        $_SESSION['quantities'] = $input;
        print "Thank you for your order.";
    }

    // The code relies on the FormHelper.php file discussed in Chapter 7. 
    // The order-form.php file referenced, which displays the form HTML, contains: ?>
    <form method="POST" action="<?= $form->encode($_SERVER['PHP_SELF']) ?>">
        <table>
            <?php if ($errors) { ?>
                <tr>
                    <td>You need to correct the following errors:</td>
                    <td>
                        <ul>
                            <?php foreach ($errors as $error) { ?>
                                <li><?= $form->encode($error) ?></li>
                            <?php } ?>
                        </ul>
                    </td>
                <?php } ?>
            <tr>
                <th>Product</th>
                <td>Quantity</td>
            </tr>
            <?php foreach ($products as $code => $name) { ?>
                <tr>
                    <td><?= htmlentities($name) ?>:</td>
                    <td><?= $form->input('text', ['name' => "quantity_$code"]) ?></td>
                </tr>
            <?php } ?>
            <tr>
                <td colspan="2" align="center"><?= $form->input('submit', ['value' => 'Order']) ?>
                </td>
            </tr>
        </table>
    </form><?php

    // The checkout page:
    session_start();
    // The same products from the order page
    
    $products = [
        'cuke' => 'Braised Sea Cucumber',
        'stomach' => "Sauteed Pig's Stomach",
        'tripe' => 'Sauteed Tripe with Wine Sauce',
        'taro' => 'Stewed Pork with Taro',
        'giblets' => 'Baked Giblets with Salt',
        'abalone' => 'Abalone with Marrow and Duck Feet'
    ];
    // Simplified main page logic without form validation
    if ($_SERVER['REQUEST_METHOD'] == 'POST') {
        process_form3();
    } else {
        // The form wasn't submitted, so display
        show_form3();
    }
    function show_form3()
    {
        global $products;
        // The "form" is just a single submit button, so we won't use
// FormHelper and just inline all the HTML here
        if (isset($_SESSION['quantities']) && (count($_SESSION['quantities']) > 0)) {
            print "<p>Your order:</p><ul>";
            foreach ($_SESSION['quantities'] as $field => $amount) {
                list($junk, $code) = explode('_', $field);
                $product = $products[$code];
                print "<li>$amount $product</li>";
            }
            print "</ul>";
            print '<form method="POST" action=' .
                htmlentities($_SERVER['PHP_SELF']) . '>';
            print '<input type="submit" value="Check Out" />';
            print '</form>';
        } else {
            print "<p>You don't have a saved order.</p>";
        }
        // This assumes the order form page is saved as "order.php"
        print '<a href="order.php">Return to Order page</a>';
    }

    function process_form3()
    {
        // This removes the data from the session
        unset($_SESSION['quantities']);
        print "<p>Thanks for your order.</p>";
    }