Interfaces and Traits

Interface Shape

Different classes can share a method shape by implementing the same interface.

shared shape The caller only needs the methods promised by the interface.

Interface Shape

width
interface_shape.php
Replay: real traced execution (multi-file project)
<?php
interface Measurable
{
    public function measure(): int;
}

class Rectangle implements Measurable
{
    public function __construct(private int $width, private int $height)
    {
    }

    public function measure(): int
    {
        return $this->width * $this->height;
    }
}

$width = 4;
$shape = new Rectangle($width, 3);
$area = $shape->measure();

echo "width=" . $width . "\n";
echo "area=" . $area . "\n";

<?php
interface Measurable
{
    public function measure(): int;
}

class Rectangle implements Measurable
{
    public function __construct(private int $width, private int $height)
    {
    }

    public function measure(): int
    {
        return $this->width * $this->height;
    }
}

$width = 2;
$shape = new Rectangle($width, 3);
$area = $shape->measure();

echo "width=" . $width . "\n";
echo "area=" . $area . "\n";

<?php
interface Measurable
{
    public function measure(): int;
}

class Rectangle implements Measurable
{
    public function __construct(private int $width, private int $height)
    {
    }

    public function measure(): int
    {
        return $this->width * $this->height;
    }
}

$width = 6;
$shape = new Rectangle($width, 3);
$area = $shape->measure();

echo "width=" . $width . "\n";
echo "area=" . $area . "\n";

  1. $width ← 4

    19$width→ 4 = 4; //@width=2, 620$shape = new Rectangle($width4, 3);21$area = $shape->measure();

  2. public function __construct(private int $width, private int $height)

    8{9    public function __construct(private int $width4, private int $height3)10    {11    }

  3. $shape ← Rectangle

    19$width = 4; //@width=2, 620$shape→ Rectangle = new Rectangle($width4, 3);21$area = $shapeRectangle->measure();

  4. public function measure(): int

    13public function measure(): int14{15    return $this->width4 * $this->height3;16}

  5. $area ← 12

    20$shape = new Rectangle($width, 3);21$area→ 12 = $shapeRectangle->measure();2223echo "width=" . $width4 . "\n";24echo "area=" . $area12 . "\n";
    outputwidth=4
area=12

  1. $width ← 2

    19$width→ 2 = 2;20$shape = new Rectangle($width2, 3);21$area = $shape->measure();

  2. public function __construct(private int $width, private int $height)

    8{9    public function __construct(private int $width2, private int $height3)10    {11    }

  3. $shape ← Rectangle

    19$width = 2;20$shape→ Rectangle = new Rectangle($width2, 3);21$area = $shapeRectangle->measure();

  4. public function measure(): int

    13public function measure(): int14{15    return $this->width2 * $this->height3;16}

  5. $area ← 6

    20$shape = new Rectangle($width, 3);21$area→ 6 = $shapeRectangle->measure();2223echo "width=" . $width2 . "\n";24echo "area=" . $area6 . "\n";
    outputwidth=2
area=6

  1. $width ← 6

    19$width→ 6 = 6;20$shape = new Rectangle($width6, 3);21$area = $shape->measure();

  2. public function __construct(private int $width, private int $height)

    8{9    public function __construct(private int $width6, private int $height3)10    {11    }

  3. $shape ← Rectangle

    19$width = 6;20$shape→ Rectangle = new Rectangle($width6, 3);21$area = $shapeRectangle->measure();

  4. public function measure(): int

    13public function measure(): int14{15    return $this->width6 * $this->height3;16}

  5. $area ← 18

    20$shape = new Rectangle($width, 3);21$area→ 18 = $shapeRectangle->measure();2223echo "width=" . $width6 . "\n";24echo "area=" . $area18 . "\n";
    outputwidth=6
area=18