Classes and Objects

Constructors

A constructor initializes a new object as it is created.

initialization Constructor arguments provide the first values that an object will use.

Constructors

seat
constructors.php
Replay: real traced execution (multi-file project)
<?php
class Ticket
{
    public function __construct(public int $seat)
    {
    }

    public function label(): string
    {
        return "seat " . $this->seat;
    }
}

$seat = 12;
$label = (new Ticket($seat))->label();

echo "seat=" . $seat . "\n";
echo "label=" . $label . "\n";

<?php
class Ticket
{
    public function __construct(public int $seat)
    {
    }

    public function label(): string
    {
        return "seat " . $this->seat;
    }
}

$seat = 3;
$label = (new Ticket($seat))->label();

echo "seat=" . $seat . "\n";
echo "label=" . $label . "\n";

<?php
class Ticket
{
    public function __construct(public int $seat)
    {
    }

    public function label(): string
    {
        return "seat " . $this->seat;
    }
}

$seat = 25;
$label = (new Ticket($seat))->label();

echo "seat=" . $seat . "\n";
echo "label=" . $label . "\n";

  1. $seat ← 12

    14$seat→ 12 = 12; //@seat=3, 2515$label = (new Ticket($seat12))->label();

  2. public function __construct(public int $seat)

    3{4    public function __construct(public int $seat12)5    {6    }

  3. public function label(): string

    8public function label(): string9{10    return "seat " . $this->seat12;11}

  4. $label ← seat 12

    14$seat = 12; //@seat=3, 2515$label→ seat 12 = (new Ticket($seat12))->label();1617echo "seat=" . $seat12 . "\n";18echo "label=" . $labelseat 12 . "\n";
    outputseat=12
label=seat 12

  1. $seat ← 3

    14$seat→ 3 = 3;15$label = (new Ticket($seat3))->label();

  2. public function __construct(public int $seat)

    3{4    public function __construct(public int $seat3)5    {6    }

  3. public function label(): string

    8public function label(): string9{10    return "seat " . $this->seat3;11}

  4. $label ← seat 3

    14$seat = 3;15$label→ seat 3 = (new Ticket($seat3))->label();1617echo "seat=" . $seat3 . "\n";18echo "label=" . $labelseat 3 . "\n";
    outputseat=3
label=seat 3

  1. $seat ← 25

    14$seat→ 25 = 25;15$label = (new Ticket($seat25))->label();

  2. public function __construct(public int $seat)

    3{4    public function __construct(public int $seat25)5    {6    }

  3. public function label(): string

    8public function label(): string9{10    return "seat " . $this->seat25;11}

  4. $label ← seat 25

    14$seat = 25;15$label→ seat 25 = (new Ticket($seat25))->label();1617echo "seat=" . $seat25 . "\n";18echo "label=" . $labelseat 25 . "\n";
    outputseat=25
label=seat 25