Interfaces and Traits

Interface Contract

An interface names methods a class promises to provide.

contract Code can depend on the interface name instead of a specific class name.

Interface Contract

name
interface_contract.php
Replay: real traced execution (multi-file project)
<?php
interface Formatter
{
    public function format(string $name): string;
}

class PrefixFormatter implements Formatter
{
    public function format(string $name): string
    {
        return "hello " . $name;
    }
}

$name = "Ada";
$formatter = new PrefixFormatter();
$message = $formatter->format($name);

echo "name=" . $name . "\n";
echo "message=" . $message . "\n";

<?php
interface Formatter
{
    public function format(string $name): string;
}

class PrefixFormatter implements Formatter
{
    public function format(string $name): string
    {
        return "hello " . $name;
    }
}

$name = "Grace";
$formatter = new PrefixFormatter();
$message = $formatter->format($name);

echo "name=" . $name . "\n";
echo "message=" . $message . "\n";

<?php
interface Formatter
{
    public function format(string $name): string;
}

class PrefixFormatter implements Formatter
{
    public function format(string $name): string
    {
        return "hello " . $name;
    }
}

$name = "Rasmus";
$formatter = new PrefixFormatter();
$message = $formatter->format($name);

echo "name=" . $name . "\n";
echo "message=" . $message . "\n";

  1. $name ← Ada, $formatter ← PrefixFormatter

    15$name→ Ada = "Ada"; //@name="Grace", "Rasmus"16$formatter→ PrefixFormatter = new PrefixFormatter();17$message = $formatterPrefixFormatter->format($nameAda);

  2. public function format(string $name): string

    8{9    public function format(string $nameAda): string10    {11        return "hello " . $nameAda;12    }

  3. $message ← hello Ada

    16$formatter = new PrefixFormatter();17$message→ hello Ada = $formatterPrefixFormatter->format($nameAda);1819echo "name=" . $nameAda . "\n";20echo "message=" . $messagehello Ada . "\n";
    outputname=Ada
message=hello Ada

  1. $name ← Grace, $formatter ← PrefixFormatter

    15$name→ Grace = "Grace";16$formatter→ PrefixFormatter = new PrefixFormatter();17$message = $formatterPrefixFormatter->format($nameGrace);

  2. public function format(string $name): string

    8{9    public function format(string $nameGrace): string10    {11        return "hello " . $nameGrace;12    }

  3. $message ← hello Grace

    16$formatter = new PrefixFormatter();17$message→ hello Grace = $formatterPrefixFormatter->format($nameGrace);1819echo "name=" . $nameGrace . "\n";20echo "message=" . $messagehello Grace . "\n";
    outputname=Grace
message=hello Grace

  1. $name ← Rasmus, $formatter ← PrefixFormatter

    15$name→ Rasmus = "Rasmus";16$formatter→ PrefixFormatter = new PrefixFormatter();17$message = $formatterPrefixFormatter->format($nameRasmus);

  2. public function format(string $name): string

    8{9    public function format(string $nameRasmus): string10    {11        return "hello " . $nameRasmus;12    }

  3. $message ← hello Rasmus

    16$formatter = new PrefixFormatter();17$message→ hello Rasmus = $formatterPrefixFormatter->format($nameRasmus);1819echo "name=" . $nameRasmus . "\n";20echo "message=" . $messagehello Rasmus . "\n";
    outputname=Rasmus
message=hello Rasmus