La programmation orientée objet en PHP

<?php
class Eleve
{
    public string $prenom;
    public array $notes = [];

    public function __construct(string $prenom)
    {
        $this->prenom = $prenom;
    }

    public function ajouterNote(float $note): void
    {
        $this->notes[] = $note;
    }

    public function moyenne(): float
    {
        return round(array_sum($this->notes) / count($this->notes), 2);
    }
}

$lea = new Eleve('Léa');
$lea->ajouterNote(5.5);
$lea->ajouterNote(5);
$noah = new Eleve('Noah');
$noah->ajouterNote(3);
echo $lea->prenom, ' : ', $lea->moyenne(), "\n";
echo $noah->prenom, ' : ', $noah->moyenne(), "\n";

Léa : 5.25
Noah : 3

<?php
class Eleve
{
    public function __construct(public string $prenom) {}
}

$a = new Eleve('Léa');
$b = $a;                  // le même objet
$b->prenom = 'Lina';
echo $a->prenom, "\n";

$c = clone $a;            // un nouvel objet, copie de $a
$c->prenom = 'Zoé';
echo $a->prenom, "\n";
var_dump($a === $b, $a === $c);

Lina
Lina
bool(true)
bool(false)

<?php
class Compte
{
    private float $solde = 0;

    public function deposer(float $montant): void
    {
        if ($montant <= 0) {
            throw new InvalidArgumentException('Montant positif attendu');
        }
        $this->solde += $montant;
    }

    public function retirer(float $montant): void
    {
        if ($montant > $this->solde) {
            throw new RuntimeException('Solde insuffisant');
        }
        $this->solde -= $montant;
    }

    public function solde(): float
    {
        return $this->solde;
    }
}

$compte = new Compte();
$compte->deposer(200);
$compte->retirer(50);
echo $compte->solde(), "\n";
try {
    $compte->retirer(500);
} catch (RuntimeException $e) {
    echo 'Refusé : ', $e->getMessage(), "\n";
}
$compte->solde = 1000000;   // interdit depuis l'extérieur

150
Refusé : Solde insuffisant
Fatal error: Uncaught Error: Cannot access private property Compte::$solde

<?php
class Compte
{
    protected float $solde = 0;

    public function deposer(float $montant): void
    {
        $this->solde += $montant;
    }

    public function solde(): float
    {
        return $this->solde;
    }
}

class CompteEpargne extends Compte
{
    public function __construct(private float $taux) {}

    public function ajouterInterets(): void
    {
        $this->deposer(round($this->solde * $this->taux, 2));
    }
}

$e = new CompteEpargne(0.0125);   // taux fictif de 1,25 %
$e->deposer(1000);
$e->ajouterInterets();
echo $e->solde(), "\n";
var_dump($e instanceof Compte);

1012.5
bool(true)

<?php
interface Forme
{
    public function aire(): float;
}

class Rectangle implements Forme
{
    public function __construct(private float $l, private float $h) {}

    public function aire(): float
    {
        return $this->l * $this->h;
    }
}

class Cercle implements Forme
{
    public function __construct(private float $r) {}

    public function aire(): float
    {
        return round(M_PI * $this->r ** 2, 2);
    }
}

function aireTotale(array $formes): float
{
    $total = 0;
    foreach ($formes as $f) {
        $total += $f->aire();   // chaque objet répond à sa façon
    }
    return $total;
}

echo aireTotale([new Rectangle(3, 4), new Cercle(1)]);

15.14

<?php
$pdo = new PDO('sqlite::memory:');   // MySQL : 'mysql:host=localhost;dbname=ecole;charset=utf8mb4'
$pdo->exec("CREATE TABLE eleves (id INTEGER PRIMARY KEY, prenom TEXT, classe TEXT)");
$pdo->exec("INSERT INTO eleves (prenom, classe) VALUES ('Léa', '2M3'), ('Noah', '2M3'), ('Elias', '2M1')");

$classe = $_GET['classe'] ?? '2M3';   // vient de l'URL : jamais collé dans le SQL
$stmt = $pdo->prepare('SELECT prenom FROM eleves WHERE classe = :classe ORDER BY prenom');
$stmt->execute(['classe' => $classe]);
foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $ligne) {
    echo htmlspecialchars($ligne['prenom']), "\n";
}

Léa
Noah

<?php
$pdo = new PDO('sqlite::memory:');
$pdo->exec("CREATE TABLE eleves (id INTEGER PRIMARY KEY, prenom TEXT, classe TEXT)");
$pdo->exec("INSERT INTO eleves (prenom, classe) VALUES ('Léa', '2M3'), ('Noah', '2M3'), ('Elias', '2M1')");
$classe = "' OR '1'='1";

// DANGER : la saisie est collée dans la requête
$sql = "SELECT prenom FROM eleves WHERE classe = '$classe' ORDER BY prenom";
foreach ($pdo->query($sql) as $ligne) {
    echo $ligne['prenom'], "\n";
}

// Requête préparée : la saisie reste une valeur
$stmt = $pdo->prepare('SELECT prenom FROM eleves WHERE classe = :classe ORDER BY prenom');
$stmt->execute(['classe' => $classe]);
echo count($stmt->fetchAll()), " ligne(s)\n";

Elias
Léa
Noah
0 ligne(s)