Session 13 - Server-Side, Part 1

Harvard Extension School
Fall 2023

Course Web Site: https://cscie12.dce.harvard.edu/

Topics

Presentation contains 32 slides

Announcements

Office Hours - Appointment and Open. Check out the schedule for the upcoming week for office hours -- there are "open / drop-in" times as well as 20 minute scheduled appointments.
Final Project information, including GitHub repo info (optional), example report, and submission parts published.
Wednesday, December 20. Final Project Due and Final Project Presentations [Optional]

Final Project Notes and Observations

Implement only three parts.
- The rest doesn't have to exist
- Use href="#" to link to those things that don't exist yet

File structure organization:

All of your html files at the top level
directory/folder for images, styles, and scripts

  .
  |-- index.html
  |-- hello-harvard.html
  |-- images
  |   |-- harvard.jpg
  |   `-- world.jpg
  |-- scripts
  |   `-- map.js
  `-- styles
      `-- site.css

lowercase file names and without spaces
- Better: my_favorite_teas.html
- Worse: My Favorite Teas.html
Within your site, use relative URL links.
- NOT relative:
  1. <link rel="stylesheet" href="/Users/david/Desktop/final_project/styles/site.css"/>
  2. <link rel="stylesheet" href="/styles/site.css"/> ← this will work in VS Code "Go Live" but most likely won't when you publish your site!
Site-wide CSS Stylesheet!
One CSS stylesheet to style all of your HTML pages!

"Back end" (Server-Side) Web Development

Language	Frameworks/Platforms
JavaScript	"Back-end": Node, Express "Front-end": React, Vue, Angular, Ember
PHP	Laravel, Symfony, CodeIgniter, CakePHP PHP-based CMS: WordPress, Drupal, Joomla
Python	Django, Flask, Zope, Plone
Go	Gin, Echo, Beego, etc.

Language

Frameworks/Platforms

JavaScript

"Back-end": Node, Express
"Front-end": React, Vue, Angular, Ember

PHP

Laravel, Symfony, CodeIgniter, CakePHP

PHP-based CMS: WordPress, Drupal, Joomla

Python

Django, Flask, Zope, Plone

Gin, Echo, Beego, etc.

CSR or SSR or SSG

CSR - Client Side Rendering
e.g. JavaScript within web browser makes request for JSON data, then builds the page based on that data
SSR - Server Side Rendering
Web server hands off HTTP request to a program, and the program generates the content
SSG - Static Site Generation also Build Time Rendering (BTR)
Content is created programmatically at build time, and the static HTML content is served at time of request.

Server Side Rendering of Content (SSR)

Web Program Examples

Markup or content is embedded within a program; program embedded into markup

first.py - Python

first.py

#!/usr/bin/python3
print("Content-type: text/html\n\n")
print("<html><head><title>Hello World!</title></head>")
print("<body><h1>Hello, World!</h1></body></html>")

first.php - PHP

first.php

<?php
echo('<html><head><title>First PHP</title></head><body>');
echo('<h1>Hello!</h1>');
echo('</body></html>');
?>

second.php - PHP

second.php
program statements within markup

<?php
      $title = "Hello World!";
?>
<!DOCTYPE html>
  <head>
    <meta charset="utf-8" />
    <title><?php echo($title) ?></title>
  </head>
  <body>
    <h1><?php echo($title) ?></h1>
  </body>
</html>

A Personal Greeting

<?php
      $name = $_GET["name"];
?>
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Greeting Page</title>
  </head>
  <body>
    <h1>Hello, <?php echo($name) ?>!</h1>
  </body>
</html>

A Personal Greeting

Without a "name", present the user a form. With a name, provide a greeting.

<?php
      $name = $_GET["name"];
?>
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8"/>
    <title>Greeting Page</title>
  </head>
  <body>
    <?php
    if ($name) {
      echo("<h1>Hello, $name!</h1>");
    } else {
      echo('<h1><label for="input_name">Enter name:</label></h1>');
      echo('<form method="get">');
      echo('<input type="text" name="name" id="input_name"/>');
      echo('<br /><input type="submit" />');
      echo('<br /><input type="reset" />');
    }
?>
  </body>
</html>

PHP Example with Courses Database

https://cscie12.dce.harvard.edu/cgi/ext-courses/departments.php

courses

Harvard Extension Course Data

Course Data in a Spreadsheet

course data loaded in a spreadsheet

Data Table in a Relational Database

RDBMS = Relational Database Management System

Postgres
MySQL
Oracle
Microsoft SQL Server

Course Data in RDBMS Table

Course data for Faculty of Arts & Sciences is in a mysql database on cscie12students (username: class; database name: coursecatalog)

SQL:

describe ext_courses

Terminal:

cscie12students$ mysql -u class coursecatalog
Welcome to the MySQL monitor.  Commands end with ; or \g.

mysql> describe ext_courses;
+----------------------+--------------+------+-----+---------+-------+
| Field                | Type         | Null | Key | Default | Extra |
+----------------------+--------------+------+-----+---------+-------+
| academic_year        | year         | YES  |     | NULL    |       |
| term                 | varchar(32)  | YES  |     | NULL    |       |
| term_code            | int          | YES  |     | NULL    |       |
| course_code          | int          | YES  |     | NULL    |       |
| course_number        | int          | YES  |     | NULL    |       |
| short_title          | text         | YES  |     | NULL    |       |
| title                | text         | YES  |     | NULL    |       |
| faculty_description  | text         | YES  |     | NULL    |       |
| department_code      | varchar(15)  | YES  |     | NULL    |       |
| department           | varchar(200) | YES  |     | NULL    |       |
| course_type          | varchar(100) | YES  |     | NULL    |       |
| credits              | varchar(50)  | YES  |     | NULL    |       |
| credit_undergraduate | int          | YES  |     | NULL    |       |
| credit_graduate      | int          | YES  |     | NULL    |       |
| url                  | varchar(300) | YES  |     | NULL    |       |
| days_of_week         | varchar(100) | YES  |     | NULL    |       |
| start_time           | varchar(15)  | YES  |     | NULL    |       |
| end_time             | varchar(15)  | YES  |     | NULL    |       |
| location             | varchar(64)  | YES  |     | NULL    |       |
| notes                | text         | YES  |     | NULL    |       |
| description          | text         | YES  |     | NULL    |       |
+----------------------+--------------+------+-----+---------+-------+
21 rows in set (0.00 sec)

Selecting List of Departments

SQL Input:

select DISTINCT department_code, department from ext_courses

Terminal Output:

mysql> SELECT DISTINCT department_code, department FROM ext_courses ORDER BY department;
+-----------------+--------------------------------------+
| department_code | department                           |
+-----------------+--------------------------------------+
| AAAS            | African and African American Studies |
| ANTH            | Anthropology and Archaeology         |
| APMA            | Applied Mathematics                  |
| ARAB            | Arabic                               |
| ASTR            | Astronomy                            |
| BIOS            | Biological Sciences                  |
| BIOT            | Biotechnology                        |
| CELT            | Celtic Languages and Literatures     |
| CHEM            | Chemistry                            |
| CLAS            | Classics                             |
| CSCI            | Computer Science                     |
| CREA            | Creative Writing                     |
| DEVP            | Development Practice                 |
| DGMD            | Digital Media                        |
| DRAM            | Dramatic Arts                        |
| ECON            | Economics                            |
| EDUC            | Education                            |
| ENSC            | Engineering Sciences                 |
| ENGL            | English                              |
| ENVR            | Environmental Studies                |
| EXPO            | Expository Writing                   |
| FREN            | French Language and Literature       |
| GERM            | German                               |
| GOVT            | Government                           |
| CGRK            | Greek                                |
| HIST            | History                              |
| HARC            | History of Art and Architecture      |
| HUMA            | Humanities                           |
| IORP            | Industrial-Organizational Psychology |
| ISMT            | Information Systems Management       |
| ITAL            | Italian                              |
| JAPA            | Japanese                             |
| JOUR            | Journalism                           |
| LATI            | Latin                                |
| LSTU            | Legal Studies                        |
| MGMT            | Management                           |
| MATH            | Mathematics                          |
| MUSE            | Museum Studies                       |
| MUSI            | Music                                |
| NUTR            | Nutrition                            |
| PHIL            | Philosophy                           |
| PHYS            | Physics                              |
| PSYC            | Psychology                           |
| RELI            | Religion                             |
| SSCI            | Social Sciences                      |
| SOCI            | Sociology                            |
| SPAN            | Spanish Language and Literature      |
| SPCH            | Speech                               |
| STAT            | Statistics                           |
| STAR            | Studio Arts and Film                 |
+-----------------+--------------------------------------+
50 rows in set (0.01 sec)

PHP Script to Connect to Database and Get List of Departments

<?php

// set header for text content
header('Content-type: text/plain');

// use Dotenv to load database info from .env file
// DB_HOST, DB_USER, DB_PW, DB_NAME
require_once('vendor/autoload.php');
$dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
$dotenv->safeLoad();

// Connecting, selecting database
$mysqli = new mysqli($_ENV['DB_HOST'],$_ENV['DB_USER'],$_ENV['DB_PW'],$_ENV['DB_NAME']);
if ($mysqli->connect_errno) {
    echo "Failed to connect to mysql: ".$mysqli->connect_errno." ".$mysqli->connect_error;
}

// Performing SQL query
$query = 'SELECT DISTINCT department, department_code FROM ext_courses ORDER BY department';
$result = $mysqli->query($query);

// iterating through results
while ($row = $result->fetch_assoc()){
  echo $row['department_code'];
  echo "\t";
  echo $row['department'];
  echo "\n";
}
?>

Output

[dph445@cs12:~/www-cscie12/html/cgi/ext-courses$ php dept-txt.php
AAAS	African and African American Studies
ANTH	Anthropology and Archaeology
APMA	Applied Mathematics
ARAB	Arabic
ASTR	Astronomy
BIOS	Biological Sciences
BIOT	Biotechnology
CELT	Celtic Languages and Literatures
CHEM	Chemistry
CLAS	Classics
CSCI	Computer Science
CREA	Creative Writing
DEVP	Development Practice
DGMD	Digital Media
DRAM	Dramatic Arts
ECON	Economics
EDUC	Education
ENSC	Engineering Sciences
ENGL	English
ENVR	Environmental Studies
EXPO	Expository Writing
FREN	French Language and Literature
GERM	German
GOVT	Government
CGRK	Greek
HIST	History
HARC	History of Art and Architecture
HUMA	Humanities
IORP	Industrial-Organizational Psychology
ISMT	Information Systems Management
ITAL	Italian
JAPA	Japanese
JOUR	Journalism
LATI	Latin
LSTU	Legal Studies
MGMT	Management
MATH	Mathematics
MUSE	Museum Studies
MUSI	Music
NUTR	Nutrition
PHIL	Philosophy
PHYS	Physics
PSYC	Psychology
RELI	Religion
SSCI	Social Sciences
SOCI	Sociology
SPAN	Spanish Language and Literature
SPCH	Speech
STAT	Statistics
STAR	Studio Arts and Film

Turn this into HTML Output

<?php
// use Dotenv to load database info from .env file
// DB_HOST, DB_USER, DB_PW,     DB_NAME
// host,    user,    password,  database name
require_once('vendor/autoload.php');
$dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
$dotenv->safeLoad();

// Connecting, selecting database
$mysqli = new mysqli($_ENV['DB_HOST'],$_ENV['DB_USER'],$_ENV['DB_PW'],$_ENV['DB_NAME']);
if ($mysqli->connect_errno) {
    echo "Failed to connect to mysql: ".$mysqli->connect_errno." ".$mysqli->connect_error;
}

// Performing SQL query
$query = <<<ENDQUERY
SELECT
    DISTINCT department, department_code
FROM
    ext_courses
ORDER BY
    department
ENDQUERY;

$result = $mysqli->query($query);

// iterating through results
echo "<ul>\n";
while ($row = $result->fetch_assoc()) {
  echo "<li>";
    echo $row['department'];
    echo "</li>\n";
 }
echo "</ul>\n";

// cleanup query result and close connection
$query_result->free();
$mysqli->close();
?>

The entire "departments-simple.php"

https://cscie12.dce.harvard.edu/cgi/ext-courses/departments-simple.php

<!DOCTYPE html>
<html>
 <head>
  <title>Departments</title>
  <link rel="stylesheet" href="styles/site.css" />
 </head>
 <body>
<h1>Harvard Extension School</h1>
<h2>Departments</h2>

<?php
// use Dotenv to load database info from .env file
// DB_HOST, DB_USER, DB_PW, DB_NAME
require_once('vendor/autoload.php');
$dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
$dotenv->safeLoad();

// Connecting, selecting database
$mysqli = new mysqli($_ENV['DB_HOST'],$_ENV['DB_USER'],$_ENV['DB_PW'],$_ENV['DB_NAME']);
if ($mysqli->connect_errno) {
    echo "Failed to connect to mysql: ".$mysqli->connect_errno." ".$mysqli->connect_error;
}

// Performing SQL query
$query = <<<ENDQUERY
SELECT
    DISTINCT department, department_code
FROM
    ext_courses
ORDER BY
    department
ENDQUERY;

$result = $mysqli->query($query);

// iterating through results
echo "<ul>\n";
while ($row = $result->fetch_assoc()) {
  echo "<li>";
    echo $row['department'];
    echo "</li>\n";
 }
echo "</ul>\n";

// cleanup query result and close connection
$query_result->free();
$mysqli->close();
?>

<footer>
  <p>This is a learning example to demonstrate PHP and mysql for the courses CSCI E-12 and CSCI S-12 taught by David Heitmeyer.  <br/>
The real <a href="https://courses.dce.harvard.edu/">Harvard Extension School course search</a> is at: <a href="https://courses.dce.harvard.edu/">courses.dce.harvard.edu</a></p>
</footer>
 </body>
</html>

Adding another view - Department Course Listings

Create another PHP file that displays course information based upon a department_code parameter.

courses.php - take a "department_code" parameter and produce alist of courses for that department.

Need to link to to courses.php:

Modify the department listing to include the hyperlink:


// Printing results in HTML
echo "<ul>\n";
while ($row = $result->fetch_assoc()) {
  echo "<li>";
  echo "<a href=\"courses.php?department_code=$row[department_code]\">"
  echo "$row[department]"
  echo "</a>";
  echo "</li>\n";
}
echo "</ul>\n";

courses.php

<!DOCTYPE html>
<html>
 <head>
  <meta charset="UTF-8"/>
  <title>Harvard Extension Courses</title>
  <link rel="stylesheet" href="styles/site.css" type="text/css"/>
 </head>
 <body>
<h1>Harvard Extension Courses</h1>
<p><a href="departments.php">Return to Department List</a></p>
<?php

// use Dotenv to load database info from .env file
// DB_HOST, DB_USER, DB_PW,     DB_NAME
// host,    user,    password,  database name
require_once('vendor/autoload.php');
$dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
$dotenv->safeLoad();

// Connecting, selecting database
$mysqli = new mysqli($_ENV['DB_HOST'],$_ENV['DB_USER'],$_ENV['DB_PW'],$_ENV['DB_NAME']);
if ($mysqli->connect_errno) {
    echo "Failed to connect to mysql: ".$mysqli->connect_errno." ".$mysqli->connect_error;
}

$dept_code = $_GET['department_code'];
$sqlescaped_dept_code = $mysqli->real_escape_string($dept_code);
$dept_code_html = htmlentities($dept_code);
?>
<h2>Department - <?php echo $dept_code_html ?></h2>
<?php
// Performing SQL query
$query = <<<ENDQUERY
SELECT
  department,
  department_code,
  course_number,
  term,
  academic_year,
  short_title,
  title,
  description,
  faculty_description
FROM
  ext_courses
WHERE
  department_code = '$sqlescaped_dept_code'
ORDER BY
  department,
  course_number,
  title
ENDQUERY;

$result = $mysqli->query($query);

// Printing results in HTML

$i = 0;
while ($row = $result->fetch_assoc()) {
  // calculate year
  $academic_year_display = $row['academic_year'];
  if ($row['term'] == 'Spring' or $row['term'] == 'January') {
    $academic_year_display += 1 ;
  }

  $course_content = <<<ENDCONTENT
  <section class="course">
  <h2 class="abbrev"> $row[short_title] </h2>
  <div>
    <p class="term">$row[term] $academic_year_display</p>
    <p class="title"><strong>$row[title]</strong></p>
    <p class="faculty">$row[faculty_description]</p>
    <p class="description">$row[description]</p>
  </div>
  </section>
ENDCONTENT;
  echo($course_content);
}


// cleanup query result and close connection
$query_result->free();
$mysqli->close();
?>
<footer>
<p><a href="./">PHP/mysql example list</a></p>
    <p>This is a learning example to demonstrate PHP and mysql for the courses CSCI E-12 and CSCI S-12 taught by David Heitmeyer.  <br/>
  The real <a href="https://courses.dce.harvard.edu/">Harvard Extension School course search</a> is at: <a href="https://courses.dce.harvard.edu/">courses.dce.harvard.edu</a>
    </p>
</footer>
</body>
</html>

Separation of Concerns

Separate the data the view using templates!

PHP code connects to database and does query and gets the data
Define how to display that data with a template (generic term, not referring to <template> element) -- and in this case, we'll use Mustache templates! Handlebars syntax is compatible with Mustache!
Note that Twig is a popular template system to use with PHP.
And note that there are many other template systems, including Liquid.

{{Mustache}} Templates

{{mustache}} is another widely used template system for JavaScript (and other languages!).

mustache

Mustache Departments

Mustache Template

mustache-dept.php

PHP

<?php

  // use Dotenv to load database info from .env file
  // DB_HOST, DB_USER, DB_PW,     DB_NAME
  // host,    user,    password,  database name
  require_once('vendor/autoload.php');
  $dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
  $dotenv->safeLoad();
  
  // Connecting, selecting database
  $mysqli = new mysqli($_ENV['DB_HOST'],$_ENV['DB_USER'],$_ENV['DB_PW'],$_ENV['DB_NAME']);
  if ($mysqli->connect_errno) {
      echo "Failed to connect to mysql: ".$mysqli->connect_errno." ".$mysqli->connect_error;
  }
  
  // Performing SQL query
  $query = <<<ENDQUERY
  SELECT DISTINCT
         department,
         department_code
  FROM ext_courses
  ORDER BY department
  ENDQUERY;
  
  $result = $mysqli->query($query);
  $rows = $result->fetch_all(MYSQLI_ASSOC);
  
  $template_data['departments'] = $rows;

// Process with Mustache Template
include('lib/Mustache.php');

$m = new Mustache;
$template_file = 'mustache_templates/departments.html';
$template_contents = file_get_contents($template_file);
echo $m->render($template_contents, $template_data);

// cleanup query result and close connection
$mysqli->close();
?>

Mustache Template

mustache_templates/departments.html

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8" />
  <title>Harvard Extension School - Departments</title>
  <link rel="stylesheet" href="styles/site.css" />
</head>

<body>
  <h1>Harvard Extension School</h1>
  <h2>Departments</h2>
  <ul>
    {{#departments}}
    <li>
      <a href="mustache-courses.php?department_code={{department_code}}">{{department}}</a>
    </li>
    {{/departments}}
  </ul>

  <footer>
    <p><a href="./">PHP/mysql example list</a></p>
    <p>This is a learning example to demonstrate PHP and mysql for the courses CSCI E-12 and CSCI S-12 taught by David
      Heitmeyer. <br />
      The real <a href="https://courses.dce.harvard.edu/">Harvard Extension School course search</a> is at: <a
        href="https://courses.dce.harvard.edu/">courses.dce.harvard.edu</a>
    </p>
  </footer>
</body>

</html>

Mustache Courses

<!DOCTYPE html>
<html lang="en">

<head>
  <title>Harvard Extension Courses in {{ department_name }}</title>
  <link rel="stylesheet" href="styles/site.css" />
  <meta charset="UTF-8" />
</head>

<body>
  <h1>Harvard Extension Courses in {{ department_name }}</h1>
  <p><a href="mustache-dept.php">Return to Department List</a></p>
  <h2>{{department_name}}</h2>
  <div>
    {{#courses}}
    <section class="course">
      <h2 class="abbrev">{{ short_title }}</h2>
      <div>
        <p class="term">{{ term }} {{ academic_year_display }}</p>
        <p class="title">{{ title }}</p>
        <p class="faculty">{{ faculty_description }}</p>
        <p class="description">{{{ description }}}</p>
      </div>
      </section>
    {{/courses}}
  </div>

  <footer>
    <p><a href="./">PHP/mysql example list</a></p>
    <p>This is a learning example to demonstrate PHP and mysql for the courses CSCI E-12 and CSCI S-12 taught by David
      Heitmeyer. <br />
      The real <a href="https://courses.dce.harvard.edu/">Harvard Extension School course search</a> is at: <a
        href="https://courses.dce.harvard.edu/">courses.dce.harvard.edu</a>
    </p>
  </footer>
</body>

</html>

Improving the Hello! Greeting

We started with

Without a "name", present the user a form. With a name, provide a greeting.

<?php
      $name = $_GET["name"];
?>
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Greeting Page</title>
  </head>
  <body>
    <?php
      if ($name) {
        echo("<h1>Hello, $name!</h1>");
      } else {
        echo('<h1><label for="input_name">Enter name:</label></h1>');
        echo('<form method="get">');
        echo('<input type="text" name="name" id="input_name"/>');
        echo('<br /><input type="submit" />');
        echo('<br /><input type="reset" />');
      }
    ?>
  </body>
</html>

Hello! Greeting, Improved

Three files: one code; two templates

index.php
greeting.html
form.html

index.php

<?php
$name = $_GET["name"];

// figure out which template is needed
if ($name) {
  $template_file = 'greeting.html';
} else {
  $template_file = 'form.html';
}
$template_contents = file_get_contents($template_file);
$template_data['name'] = $name;

// Process with Mustache Template
include('lib/Mustache.php');
$m = new Mustache;

echo $m->render($template_contents, $template_data);

?>

greeting.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Greeting Page for {{name}}</title>
  </head>
  <body>
      <h1>Hello, {{name}}!</h1>
  </body>
</html>

form.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Greeting Page</title>
  </head>
  <body>
      <h1><label for="input_name">Enter name:</label></h1>
      <form method="get">
      <input type="text" name="name" id="input_name"/>
      <br /><input type="submit" />
      <br /><input type="reset" />
  </body>
</html>

Sending Email

Mail service -- e.g. Mailgun, Sendgrid, etc.

submit.php Example (uses Mailgun)

<?php require_once 'vendor/autoload.php';

     $loader = new \Twig\Loader\FilesystemLoader('./templates');
     $twig = new \Twig\Environment($loader, [
         'cache' => './compilation_cache',
         'debug' => true,
         'auto_reload' => true
     ]);
     $requestTime = new DateTime();
     $requestTime->setTimestamp($_SERVER['REQUEST_TIME']);
     $requestTimeHuman = $requestTime->format('Y-m-d\TH:i:s');

     $echocontent = $twig->render('form-response-template.html',
          [
          'getparams' => $_GET,
          'postparams' => $_POST,
          'httpheaders' => getallheaders(),
          'httpmethod' => $_SERVER['REQUEST_METHOD'],
          'serverinfo' => $_SERVER,
          'requesttime' => $requestTimeHuman,
          'httpreferer' => $_SERVER['HTTP_REFERER']
          ]);
     ?>


     <?php

     require 'vendor/autoload.php';
     use Mailgun\Mailgun;

     $mailto = filter_var($_POST['__mailto'], FILTER_VALIDATE_EMAIL);
     $mailkey = '';
     if (preg_match('/^csci(e|s)12\-(spring|summer|fall)-\d{4}-[a-z]+[0-9]+$/',$_POST['__mailkey'])) {
        $mailkey = $_POST['__mailkey'];
     }

     // only send if POST and if __mailto and if __mailkey exist

     if (strcmp($_SERVER['REQUEST_METHOD'],'POST') == 0 && $mailto && $mailkey ) {
       error_log("FormSubmit | MAILGUN | $mailkey | $mailto |");
       // First, instantiate the SDK with your API credentials
       $MG_API_KEY = getenv('MG_API_KEY');
       $MG_DOMAIN = getenv('MG_DOMAIN');
       $MG_ = getenv('MG_');

       $mg = Mailgun::create($MG_API_KEY); // For US servers
       $domain = $MG_DOMAIN;

       // Now, compose and send your message.
       // $mg->messages()->send($domain, $params);
       $mg->messages()->send($domain, [
         ''    => $MG_,
         'to'      => $mailto,
         'subject' => 'Form Submission',
         'html'    => $echocontent
       ]);
     }

     echo($echocontent);
     ?>

form_response_template.html

This is a PHP "Twig" template.

<DOCTYPE html>
     <html lang="en">
       <head>
        <title>Form Submission</title>
        <style><!-- inline styles removed for clarity --></style>
       </head>

       <body>
         <h1>Form Submission</h1>
         {% if getparams %}
         <h2>GET Parameters</h2>
         <table>
           <thead>
             <tr><th>Name</th><th>Value</th></tr>
           </thead>
           <tbody>
           {% for key, value in getparams %}
           <tr>
             <th>{{ key }}</th>
             <td>
               {% if value is iterable %}
               {% for v in value %}
                 {{ v }}{% if not(loop.last) %},<br/>{% endif %}
               {% endfor %}
               {% else %}
                 {{ value }}
               {% endif %}
             </td>
           </tr>
           {% endfor %}
           </tbody>
         </table>
         {% endif %}

         {% if postparams %}
         <h2>POST Parameters</h2>
         <table>
           <thead>
             <tr><th>Name</th><th>Value</th></tr>
           </thead>
           <tbody>
           {% for key, value in postparams %}
           <tr>
             <th>{{ key }}</th>
             <td>
               {% if value is iterable %}
               {% for v in value %}
                 {{ v }}{% if not(loop.last) %},<br/>{% endif %}
               {% endfor %}
               {% else %}
                 {{ value }}
               {% endif %}
             </td>
           </tr>
           {% endfor %}
           </tbody>
         </table>
         {% endif %}

         {% if serverinfo %}
         <h2>Request Information</h2>
         <table>
           <thead>
             <tr><th>Name</th><th>Value</th></tr>
           </thead>
           <tbody>
             <tr><th>Request Time</th><td>{{ requesttime }}</td></tr>
             <tr><th>Remote Address</th><td>{{ serverinfo['REMOTE_ADDR'] }}</td></tr>
             <tr><th>HTTP Referrer</th><td><a href="{{ httpreferer }}">{{ httpreferer }}</a></td></tr>
             <tr><th>HTTP Method</th><td>{{ httpmethod }}</td></tr>
           </tbody>
         </table>
         {% endif %}

         <footer>
           <p>This form submission tool is only for use by current students in <a href="https://cscie12.dce.harvard.edu/">CSCI E-12</a> and <a href="https://cscis12.dce.harvard.edu/">CSCI S-12</a> courses.</p><p>David Heitmeyer | <a href="https://extension.harvard.edu/">Harvard Extension School</a> | <a href="https://summer.harvard.edu/">Harvard Summer School</a></footer>
       </body>
      </html>

CSR (Client Side Rendering)

Front-end JavaScript + templates and Back-end JSON

Departments

json-dept.php - PHP script that produces JSON
departments.html - uses Handlebars

Courses

json-courses.php?department_code=CHEM - PHP script that produces JSON
courses.html?department_code=CHEM - uses Handlebars

Getting JSON from HTTP request

JavaScript functions are often asynchronous -- the script continues to run before a step has completed!

Javascript "fetch"

fetch(url).then(response => response.json()).then(data => processData(data));

Let's Try It Out!

Apples
Courses
National Park Service

Apples

Apples - https://cscie12.dce.harvard.edu/apples-pyo.php

You may find a "JSON Viewer" plugin or extension for your browser useful if you work with JSON
json

Apples

apples-fetch.html
JSON data apples-pyo.php

The JavaScript:

let applesUrl = "https://cscie12.dce.harvard.edu/apples-pyo.php";
  document.addEventListener('DOMContentLoaded',function(){
    fetch(applesUrl)
      .then(response => response.json())
      .then(data => buildApplesList(data));
  });

  function buildApplesList(data){
    let template = document.getElementById('apple-template').innerHTML ;
    console.log(template);
    let compiledTemplate = Handlebars.compile(template);
    let rendered = compiledTemplate(data);
    document.getElementById('applelist').innerHTML = rendered;
  }

The template:

<template id="apple-template">
  <h2>Picking Now</h2>
    <ul>
      {{#apples.picking_now}}
        <li>{{ . }}
      {{/apples.picking_now}}
    </ul>

    <h2>Picking Soon</h2>
    <ul>
      {{#apples.picking_soon}}
        <li>{{ . }}
      {{/apples.picking_soon}}
    </ul>
  </template>

JS and fetch

/* mlb api;  sportId = 1 is major league */
  let urlTeams = "https://statsapi.mlb.com/api/v1/teams?sportId=1";

  document.addEventListener("DOMContentLoaded", function () {
    fetch(urlTeams)
      .then(response => response.json())
      .then(data => buildList(data.teams));
  });

Courses — PHP and JSON data

Two problems to solve here:

Producing JSON data on server side
Processing JSON data on client-side

<?php

/// use Dotenv to load database info  .env file
// DB_HOST, DB_USER, DB_PW, DB_NAME
require_once('vendor/autoload.php');
$dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
$dotenv->safeLoad();

// Connecting, selecting database
$mysqli = new mysqli($_ENV['DB_HOST'],$_ENV['DB_USER'],$_ENV['DB_PW'],$_ENV['DB_NAME']);
if ($mysqli->connect_errno) {
    echo "Failed to connect to mysql: ".$mysqli->connect_errno." ".$mysqli->connect_error;
}

$dept_code = $_GET['department_code'];
$sqlescaped_dept_code = $mysqli->real_escape_string($dept_code);

// Performing SQL query
$query = <<<ENDQUERY
SELECT
  department,
  department_code,
  course_number,
  term,
  academic_year,
  short_title,
  title,
  description,
  faculty_description

  ext_courses
WHERE
  department_code = '$sqlescaped_dept_code'
ORDER BY
  department,
  course_number,
  title
ENDQUERY;

$query_result = $mysqli->query($query);

$i = 0;
while ($row = $query_result->fetch_assoc()) {
  // calculate year
  $academic_year_display = $row['academic_year'];
  if ($row['term'] == 'Spring' or $row['term'] == 'January') {
    $academic_year_display += 1 ;
  }
  $row['academic_year_display'] = $academic_year_display;

  $results[$i++] = $row;
}

$template_data['courses'] = $results;
$template_data['department_name'] = $dept_code;

header('Content-type: application/json');
echo json_encode($template_data);

// cleanup query result and close connection
$query_result->free();
$mysqli->close();
?>

Front-end courses

For example: CSCI courses (courses.html?department_code=CSCI)

Use JavaScript fetch to get the JSON data
Use Handlebars to process the data

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8" />
  <title>Departments</title>
  <link rel="stylesheet" href="styles/site.css" />
  <script src="https://cdnjs.cloudflare.com/ajax/libs/handlebars.js/4.7.7/handlebars.min.js"
    integrity="sha512-RNLkV3d+aLtfcpEyFG8jRbnWHxUqVZozacROI4J2F1sTaDqo1dPQYs01OMi1t1w9Y2FdbSCDSQ2ZVdAC8bzgAg=="
    crossorigin="anonymous"></script>

  <script>
    let dataUrl = './json-courses.php';
    let urlParams = new URLSearchParams(window.location.search);
    console.log(urlParams.get('department_code'));
    let department_code = urlParams.get('department_code');
    document.addEventListener('DOMContentLoaded', function () {
      fetch(dataUrl + '?department_code=' + department_code)
        .then(response => response.json())
        .then(data => {
          console.log(data);
          let mysource = document.getElementById('courses-list-template').innerHTML;
          let mytemplate = Handlebars.compile(mysource);
          let myresult = mytemplate(data)
          document.getElementById('courses-list').innerHTML = myresult;
        });
    });
  </script>

</head>

<body>
  <h1>Harvard Extension School</h1>
  <p><a href="departments.html">Return to Department List</a></p>

  <div id="courses-list">

  </div>

  <div id="courses-list-template" class="handlebars">
    <h2>{{ department_name }}</h2>
    <p>{{ courses.length }} courses</p>
    <div>
      {{#courses}}
      <section class="course">
        <h2 class="abbrev">{{ short_title }}</h2>
        <div>
          <p class="term">{{ term }} {{ academic_year_display }}</p>
          <p class="title">{{ title }}</p>
          <p class="faculty">{{ faculty_description }}</p>
          <p class="description">{{{ description }}}</p>
        </div>
      </section>
      {{/courses}}
    </div>

    <footer>
      <p><a href="./">PHP/mysql example list</a></p>
      <p>This is a learning example to demonstrate PHP and mysql for the courses CSCI E-12 and CSCI S-12 taught by David
        Heitmeyer. <br />
        The real <a href="https://courses.dce.harvard.edu/">Harvard Extension School course search</a> is at: <a
          href="https://courses.dce.harvard.edu/">courses.dce.harvard.edu</a>
      </p>
    </footer>

</body>

</html>

Next Time

JavaScript Frameworks that can make this easier!
Build time rendering (BTR) or Static Site Generation (SSG) approach!
Punch list of things you should have heard about before completing an intro web development class!