Introduction to

programming

April 2019

By Loïc TRUCHOT

Featuring PHP

The perfect stack

for a 2019 web programmer

PHP / MySQL (+ Laravel, Zend or Symphony...)
Node.js / MongoDB
Wordpress

HTML
CSS (+ SASS)
JavaScript (+ React, Angular or Vue...)

Bonus : Bootstrap, JQuery

About PHP

Very classic
Server-side language to produce dynamic website
Paradigm: Procedural (imperative) + Object Oriented
Interpreted when page is asked (not compiled before)
80% of the web
- Facebook, Dailymotion, Wikipedia, WordPress, Slack...
Current version: 7.4
What does PHP do finally ?
- It generate HTML page with
  - dynamic parts, changing for each user, content, URL
  - static parts, reusing all common contents, like headers, footers, left menu...
  - server operation (calcul, database, CRUD, sessions, API...)

Install & run PHP

As any language, PHP must be installed
As any webserver, PHP should ran in background
3 alternatives: EasyPHP, Wamp, Xampp
Let's try EasyPHP, the simplest...
- https://www.easyphp.org
- download the 17.0 DevServer for Windows 10
- install it (as administrator if needed), say "yes" and "next" to everything
- run, and find the logo in your main status bar

Use the REPL

open the dashboard
PHP code tester: a Read-Eval-Print Loop
click "interpret", then describe what you see
clean the PHP code tester
add a <h1></h1>, name your Pizzeria here
add a <h2></h2>, say "hello" to your neighbor here
click "Interpret" button

Variables

What is "variable" here ?
Let's add this new code (now, never press "stop" again)
replace first variable with <?php echo 'variable'; ?>
click "Interpret" button

<h1>Pizza YOLO</h1>
<h2>Hello Sonia !</h2>
<p>
    Today is friday: week-end is coming.<br />
    What about a delicious Pizza tonight, Sonia ?
</p>
<div>
    Try our classics :
    <ul>
        <li>Vegeteriana</li>
        <li>Il Diavolo</li>
        <li>Quattro Formagi</li>
    </ul>
    Or choose the daily chef choice:
    <strong>the Calzone</strong>
</div>
<p>
    <em>Pizza price: 10 € - See you soon Sonia.</em>
</p>

step 1

Variables

declare the $name variable
Assign it the value "Sonia"
replace the "Sonia" part, after echo, with your own variable
click "Interpret" button

<?php 
    $name;
?>
<h1>Pizza YOLO</h1>
<h2>Hello <?php echo "Sonia"; ?> !</h2>

step 2

To remember

PHP code is mixed with the HTML
The PHP markup is <?php ... ?>
echo is a PHP function that "print" anything in the HTML
a PHP variable begin with the sign "$", like in $myVar
a PHP statement always end with a ";"
a variable assignment is done with the "="
full exemple :

<?php 
    $name = "Sonia";
?>
<h1>Pizza YOLO</h1>
<h2>Hello <?php echo $name ?> !</h2>

Let's migrate to

a real file index.php

Copy contents to an index.php file
Create a folder for your project (without accents or whitespaces, like C:\php\pizza), put your file inside
Stop the REPL
Add your folder as working dir in EasyPHP dashboard
Start the HTTP Server, click the link-name of your project
Let's examine the result
Use sublime-text / vs-code to open the folder
Do some change in index.php, then press [F5]

Workshop session

variables

Open index.php with Sublime Text / VS Code
Replace every variables texts with some new variables like $name

Variables

string -> concatenations

<?php 
    $firstname = "Samir";
    $lastname = "Hanini";
?>
<h1>Pizza YOLO</h1>
<h2>Hello <?php echo $firstname; ?> !</h2>

step 3

Types

Integer or Float -> calculations

<?php 
    $nbOfPizza = 5;
    $price = 10;
    $discount = 0.2;
?>
<strong>Total: </strong>

boolean -> conditions

<?php
    $isConnected = true;
    $hasDiscount = true;
?>
<strong>Is connected and has discount : </strong>

To remember

A variable is useful for :
- replace part of the page that can change (ex: a name)
- store repeated pattern (ex: an info displayed 3 times)
- store temporary needed value (ex: a discount multiplier)
A variable is like a box, we can change what is inside
- $price = 10;
  - before " = ", the left part is the box
  - after " = ", the right part is the new value we put inside
When PHP is interpreted, right part variables are evaluated, replaced by its value
- $price = $price * 3 + $price;
  - $price value is now 40
Each value have a "type" (string, number, boolean, etc)
Each type has different operations (concat, add, compare, etc)

Control structures

Logical conditions

if (boolean) { thenDoThis( ); }
else { otherwiseDoThat(); }
Operators: &&, ||, <, <=, >, >=, ==, !=, !
elseif, for multiple possibilities
Coercion: 0, "", null...
,

<?php 
    $name;
?>
<h1>PHPizza</h1>
<?php 
    if (isset($name)) {
        echo "<h2>Hello $name !</h2>";
    } else { 
        echo "Please, <button>log in</button>";
    }
?>

step 1

Workshop session

if else

Apply different discount to total
- not set -> nothing
- less than 20€ -> nothing
- between 20€ & 30€ -> 10%
- between 31€ & 50€ -> 20%
- more than 50€ -> 30%

Logical conditions

switch ($var) { }
list every possibilities:
- case "value 1":
  - doThis();
  - break;
- case "value 2":
  - doThat();
  - break;
add default possibility:
- default:
  - doDefault();

<?php 
    $discountCode = "abc"; 
    $isLogin = false;
    $name;
    echo "<header>Hello "  
        . ($isLogin ? $name : "you") 
        . "</header>";
    switch ($discountCode) {
        case "abc":
            echo "10€ de réduction";
            break;
        case "def":
            echo "20€ de réduction";
            break;
        default:
            echo "Pas de réduction";
    }
?>

step 2

Ternary :
- true ? whenTrue(); : whenFalse();

Workshop session

switch

Apply a different discount for 4 differents codes
If no discount code, apply 1€ discount
In all case, minimal price is 10€ (use ternary condition)

To remember

if / else is the basic block of any computer program
It needs a boolean, or anything convertible to boolean
A shorter way exists : the ternary operator, x ? a : b;
elseif for extra conditions
first condition fullfilled is the one
switch for several values of the same var

Loops

A recursive "if"
Do it until something becomes false: "while (boolean) { }"
Why some loop can freeze the computer ?

<?php 
$x = 1; 

while($x <= 5) {
    echo "The number is: $x <br>";
    $x++;
} 
?>

step 1

Workshop session

while

Create a loop for our working pizzaïolos
- it display x times "A new pizza was just bought."
- after half times reached, it says "Keep going: half done !"

Loops

the for loop, with start & end conditions
for (start; condition; operation) { }
The most popular : force to think to the ending condition

<?php 
    for($x = 1; $x <= 5; $x++) {
        echo "The number is: $x <br>";   
    } 
?>

step 2

Workshop session

for

rand(1, 100) return an integer between 1 and 100
our curstomers have 30% chance to win a discount
generate 100 draws, and display win & lose in a <ul>

To remember

while is the classical loop: work like a if, but repeated until condition is false
so you MUST think about the end of the loop
that's why for loop is mostly used: start, end, change are described directly
rand(x, y); is a PHP function to get a random number

To finally remember

A computer can :
- store / memoize (variables)
- calculate / combine (operations)
- compare (conditions)
- repeat / iterate (loops)

Refacto time

comment your code with // and /* */
put everything in a proper HTML doc
add bootstrap and some prettier classes

Data structures

Array

array = super variable containing several elements, like a shelf of boxes
So it's a list of data
- $list1 = array(4, 8, 15, 16, 23, 42);
- $list2 = array("Samir", "Sarah", "Jordan", "Anaïs");
Each data is indexed from 0 to n
We can access any "box" by its [index]
count($myArray) return the length of my array

<?php 
    $list = array("Pascal", 45, "Coach", false, "Amsterdam"); 
    echo "His name is " . $list[0] .", he live in ". $list[4];
?>

step 1

Workshop session

array

Put our list of pizza in an array
Iterate with a for loop, to display all pizzas in the <ul>
pick a random pizza as a daily choice

Array

A new loop: the foreach
With or without index

<?php 
$birds = array("cardinal", "kestrel", "kite", "mockingbird"); 

foreach($birds as $bird) {
    echo $bird . " says tweet tweet.<br />";
}
shuffle($birds);
foreach($birds as $index => $bird) {
    echo $bird . " is now n°" . $index . " in the list<br />";
}
?>

step 2

What about array of arrays ? no problem, as much as you need
And so on ??? It's just multidimensional arrays / matrix

Workshop session

array

Put your old pizzas array as first element of a new "food" array
Add an array of drinks, and an array of desserts in this food array
Display everything in <ul> with nested foreach loops
Display a title before each <ul>: Pizzas, Drinks, Desserts

PHP array functions

Remember the CRUD ?
- Create: array_push($list, "element3", "element4");
- Read: echo $list[2];
- Update: $list[2] = "new element";
- Delete: array_splice($list, 2, 1)
Some other useful tools:
- array_unshift ()
- count()
- sort(), shuffle(), array_reverse()
- array_sum()
- @see further doc when you have an idea
  - https://www.php.net/manual/en/ref.array.php

hashtables

Just like an array, but indexed by string
Unordered, but well organized
Crucial in Oriented Object Programming
foreach becomes handy

<?php 
    $person = array(
        "name" => "Pascal", 
        "age" => 45, 
        "job" => "Coach", 
        "married" => false, 
        'city' => "Amsterdam"); 
    echo "His name is " . $person["name"] .", he live in ". $person["city"];
    foreach($person as $key => $value) {
        echo "$key: $value</br>";
    }
?>

step 1

Text

keyed list, associative list, dictionary...
very similar to objects

hashtables

One of the most common data structure: the collection
Collection = array of hashtables, all formatted the same way
Just like in an excel...
Just like in a data base !

<?php 
    $person = array(
        array("first" => "Nicolas", "last" => "Cage"),
        array("first" => "John", "last" => "Travolta"),
    ); 

    foreach($person as $value) {
        echo $value["first"] . " " . $value["last"] . "</br>";
    }
?>

step 2

Workshop session

hashtables

Create a pizza object for the "vegetariana" with
- a name
- a description
- a list of ingredients
- a price
- an image (find it on Internet !)
Do the same for each pizzas, and put them in a collection
Change website code: it should work with this collection

To remember

Data stucture is: "how to store logically and efficiently my data ?"
Variables of primitives (string, boolean, number) ? Array ? Hashtables ? Collections (array of hashtables ?)
With PHP
- declaring a new array:
  - $list = array(1, 2, 3);
- declaring a new hashtable:
  - $object = array("a" => 1, "b" => 2);
In all case, use foreach to loop on it

Functions

The most important thing in computer science...
...in a human point of view
Reusable routine/subprogram
Something already existing, or something I'll build myself
Something I can bring with me all my programmer life
declaration != execution

<?php
    // declaration (nothing happen)
    function say_hello () {
        echo "hello<br/>";
    }
    // execute 2 times (write "hello<br/>" 2 times)
    say_hello();
    say_hello();
?>

step 1

Functions

A function can (should ?) :
- get some parameters (arguments)
- return something
- it's an input -> output reusable process

<?php 
    function add($a, $b) {
        return $a + $b;
    }
    echo add(3, 5);
    echo add(198708, 12349);
?>

step 2

Functions

The "return" keyword imply the end of the function

function checkToDo($isDone) {
    if ($isDone == true) { 
        return "the task is done.";
    } else {
        return "the task is not done.";
    }
    // following statement will never be evaluated
    echo "this will not happen";
}

step 3

No return function ? it will return NULL at the end: it's a special empty value

function test ($a) {
    $b = $a * 2;
    // nothing returned ?
}
echo (test(42) == NULL); // will be TRUE and log "1"

Workshop session

functions

Write a function that return the average age in the classroom
Use "round" to format this number

Workshop session

functions

Write a function that return a "card" for each pizza
Pizza can only have 2 types of meat: chicken and ham
If the pizza is vegetarian, it must appear in the card

Live coding session

bigger functions

Write a function that can perform some quizz

$quizz = array(
    array("q" => "Hélium", "a" => "He"),
    array("q" => "Oxygène", "a" => "O"),
    // and at least 2 more similar Question/Answer 
);

return a hashtable with
- a random question
- 4 shuffled answers, 3 random + the right one
- the index of the right answer

take a quizz as param

Digression about

value VS reference

Functions

Pure functions = predictible
- any input always generate the same output

function add2 ($n) {
    return $n + 2;
}
add2(2);
add2(2);

step 6

Impure functions = side effects
- done with & near params, the "reference mark"
- can change something in another part of the program

$age = 33;
function happyBirthday (&$n) {
    $n = $n + 1;
}
happyBirthday($age);
happyBirthday($age);
echo $age;

Try this code with and without & to see the difference !

To remember

Procedural languages are only about
- data stuctures (vars, arrays) and types
- control structures (if, for, foreach)
- functions
  - pures (predictible input -> ouput)
  - impures (side effects)
Oriented Object languages like PHP have more complexity:
- classes and instances
Functional languages like Haskell have less complexity:
- no control structures (replaced by functions)
- only pures functions

THANKS EVERYONE
It's finally done !

See you soon with a "Deeper PHP" module

Multiple files projects
Oriented Object PHP
PDO classe and DataBase CRUD
AJAX and Forms treatment

Introduction to programming 2019

By Loïc TRUCHOT

Introduction to programming 2019

Discovering computer science basis with some PHP examples

Loïc TRUCHOT

JavaScript Fullstack Expert & Senior web developer

github.com/ltruchot

Introduction to

programming

Featuring PHP

The perfect stack

for a 2019 web programmer

About PHP

Install & run PHP

Use the REPL

Variables

Variables

To remember

Let's migrate to

a real file index.php

Workshop session

variables

Variables

Types

To remember

Control structures

Logical conditions

Workshop session

if else

Logical conditions

Workshop session

switch

To remember

Loops

Workshop session

while

Loops

Workshop session

for

To remember

To finally remember

Refacto time

Data structures

Array

Workshop session

array

Array

Workshop session

array

PHP array functions

hashtables

hashtables

Workshop session

hashtables

To remember

Functions

Functions

Functions

Workshop session

functions

Workshop session

functions

Live coding session

bigger functions

Digression about

value VS reference

Functions

To remember

Introduction to programming 2019

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