learningPHP: Chapter-4

4_data-groups.php

<?php
// Chapter-4: Exercises

// Question-1

// 1. According to the US Census Bureau, the 10 largest American cities (by population) in 2010 were as follows:
// • New York, NY (8,175,133 people)
// • Los Angeles, CA (3,792,621)
// • Chicago, IL (2,695,598)
// • Houston, TX (2,100,263)
// • Philadelphia, PA (1,526,006)
// • Phoenix, AZ (1,445,632)
// • San Antonio, TX (1,327,407)
// • San Diego, CA (1,307,402)
// • Dallas, TX (1,197,816)
// • San Jose, CA (945,942)
// 
// Define an array (or arrays) that holds this information about locations and populations. 
// Print a table of locations and population information that includes the total population in all 10 cities.

// Answer-1 ?>

<table>
    <tr>
        <th>City</th>
        <th>Population</th>
    </tr>
    <?php
    $census = [
        'New York, NY' => 8175133,
        'Los Angeles, CA' => 3792621,
        'Chicago, IL' => 2695598,
        'Houston, TX' => 2100263,
        'Philadelphia, PA' => 1526006,
        'Phoenix, AZ' => 1445632,
        'San Antonio, TX' => 1327407,
        'San Diego, CA' => 1307402,
        'Dallas, TX' => 1197816,
        'San Jose, CA' => 945942
    ];
    $total = 0;
    foreach ($census as $city => $population) {
        $total += $population;
        print "<tr><td>$city</td><td>$population</td></tr>\n";
    }
    print "<tr><td>Total</td><td>$total</td></tr>\n";
    print "</table>";

    ?>

    <?php

    // Question-2
    
    // 2. Modify your solution to the previous exercise so that the rows in the result table are ordered by population. 
    // Then modify your solution so that the rows are ordered by city name.
    
    // Answer-2
    
    $census = [
        'New York, NY' => 8175133,
        'Los Angeles, CA' => 3792621,
        'Chicago, IL' => 2695598,
        'Houston, TX' => 2100263,
        'Philadelphia, PA' => 1526006,
        'Phoenix, AZ' => 1445632,
        'San Antonio, TX' => 1327407,
        'San Diego, CA' => 1307402,
        'Dallas, TX' => 1197816,
        'San Jose, CA' => 945942
    ];
    // Sort the associative array by value
    asort($census);
    print "<table>\n";
    print "<tr><th>City</th><th>Population</th></tr>\n";
    $total = 0;
    foreach ($census as $city => $population) {
        $total += $population;
        print "<tr><td>$city</td><td>$population</td></tr>\n";
    }
    print "<tr><td>Total</td><td>$total</td></tr>\n";
    print "</table>";
    // Sort the associative array by key
    ksort($census);
    print "<table>\n";
    print "<tr><th>City</th><th>Population</th></tr>\n";
    $total = 0;
    foreach ($census as $city => $population) {
        $total += $population;
        print "<tr><td>$city</td><td>$population</td></tr>\n";
    }
    print "<tr><td>Total</td><td>$total</td></tr>\n";
    print "</table>";

    // Question-3
    
    // 3. Modify your solution to the first exercise so that the table also contains rows that hold state population totals for each state represented in the list of cities.
    
    // Answer-3 ?>

    <table>
        <tr>
            <th>City</th>
            <th>Population</th>
        </tr><?php

        // Each element in $census is a three-element array containing city name, state, and population
        $census = [
            ['New York', 'NY', 8175133],
            ['Los Angeles', 'CA', 3792621],
            ['Chicago', 'IL', 2695598],
            ['Houston', 'TX', 2100263],
            ['Philadelphia', 'PA', 1526006],
            ['Phoenix', 'AZ', 1445632],
            ['San Antonio', 'TX', 1327407],
            ['San Diego', 'CA', 1307402],
            ['Dallas', 'TX', 1197816],
            ['San Jose', 'CA', 945942]
        ];
        $total = 0;
        $state_totals = array();
        foreach ($census as $city_info) {
            // Update the total population
            $total += $city_info[2];
            // If we haven't seen this state yet, initialize its population total to 0
            if (!array_key_exists($city_info[1], $state_totals)) {
                $state_totals[$city_info[1]] = 0;
            }
            // Update the per-state population
            $state_totals[$city_info[1]] += $city_info[2];
            print "<tr><td>$city_info[0], $city_info[1]</td><td>$city_info[2]</td></tr>\n";
        }
        print "<tr><td>Total</td><td>$total</td></tr>\n";
        // Print the per-state totals
        foreach ($state_totals as $state => $population) {
            print "<tr><td>$state</td><td>$population</td></tr>\n";
        }
        print "</table>";

        // Question-4 
        
        // 4. For each of the following kinds of information, 
        // state how you would store it in an array and then give sample code that creates such an array with a few elements.
        // For example, for the first item, you might say, “An associative array whose key is the student’s name 
        // and whose value is an associative array of grade and ID number,” as in the following:
        
        $students = [
            'James D. McCawley' => ['grade' => 'A+', 'id' => 271231],
            'Buwei Yang Chao' => ['grade' => 'A', 'id' => 818211]
        ];

        // Answer-4

        // a. The grades and ID numbers of students in a class

        /* The grades and ID numbers of students in a class:
            An associative array whose key is the student's name and whose value is an associative array of grade and ID number
        */
        $students = [ 
            'James D. McCawley' => [ 'grade' => 'A+','id' => 271231 ],
            'Buwei Yang Chao' => [ 'grade' => 'A', 'id' => 818211] 
        ];

        // b. How many of each item in a store inventory are in stock

        /* How many of each item in a store inventory are in stock:
            An associative array whose key is the item name and whose value is the number in stock
        */
        $inventory = [ 'Wok' => 5, 'Steamer' => 3, 'Heavy Cleaver' => 3, 'Light Cleaver' => 0 ];

        // c. School lunches for a week: the different parts of each meal (entrée, side dish, drink, etc.) and the cost for each day

        /* School lunches for a week — the different parts of each meal (entree, side dish, drink, etc.) and the cost for each day:
            An associative array whose key is the day and whose value is an associative array describing the meal. 
            This associative array has a key/value pair for cost and a key/value pair for each part of the meal.
        */
        $lunches = [ 
            'Monday' => [ 
                'cost' => 1.50,
                'entree' => 'Beef Shu-Mai',
                'side' => 'Salty Fried Cake',
                'drink' => 'Black Tea' 
            ],
            'Tuesday' => [ 
                'cost' => 2.50,
                'entree' => 'Clear-steamed Fish',
                'side' => 'Turnip Cake',
                'drink' => 'Bubble Tea' 
            ],
            'Wednesday' => [ 
                'cost' => 2.00,
                'entree' => 'Braised Sea Cucumber',
                'side' => 'Turnip Cake',
                'drink' => 'Green Tea' 
            ],
            'Thursday' => [ 
                'cost' => 1.35,
                'entree' => 'Stir-fried Two Winters',
                'side' => 'Egg Puff',
                'drink' => 'Black Tea' 
            ],
            'Friday' => [ 
                'cost' => 3.25,
                'entree' => 'Stewed Pork with Taro',
                'side' => 'Duck Feet',
                'drink' => 'Jasmine Tea' 
            ] 
        ];

        // d. The names of people in your family

        /* The names of people in your family:
            A numeric array whose indices are implicit and whose values are the names of family members
        */
        $family = [ 'Bart', 'Lisa', 'Homer', 'Marge', 'Maggie' ];

        // e. The names, ages, and relationship to you of people in your family

        /* The names, ages, and relationship to you of people in your family:
            An associative array whose keys are the names of family members and whose
            values are associative arrays with age and relationship key/value pairs
        */
        $family = [ 
            'Bart' => [ 
                'age' => 10,
                'relation' => 'brother' 
            ],
            'Lisa' => [ 
                'age' => 7,
                'relation' => 'sister' 
            ],
            'Homer' => [ 
                'age' => 36,
                'relation' => 'father' 
            ],
            'Marge' => [ 
                'age' => 34,
                'relation' => 'mother' 
            ],
            'Maggie' => [ 
                'age' => 1,
                'relation' => 'self' 
            ] 
        ];