Trait State

A trait can provide methods that update state stored on the object.

trait_state.php

<?php
trait CountsItems
{
    private int $count = 0;

    public function add(int $items): int
    {
        $this->count = $this->count + $items;
        return $this->count;
    }
}

class Basket
{
    use CountsItems;
}

$items = ;
$basket = new Basket();
$total = $basket->add($items);

echo "items=" . $items . "\n";
echo "total=" . $total . "\n";

<?php
trait CountsItems
{
    private int $count = 0;

    public function add(int $items): int
    {
        $this->count = $this->count + $items;
        return $this->count;
    }
}

class Basket
{
    use CountsItems;
}

$items = ;
$basket = new Basket();
$total = $basket->add($items);

echo "items=" . $items . "\n";
echo "total=" . $total . "\n";

<?php
trait CountsItems
{
    private int $count = 0;

    public function add(int $items): int
    {
        $this->count = $this->count + $items;
        return $this->count;
    }
}

class Basket
{
    use CountsItems;
}

$items = ;
$basket = new Basket();
$total = $basket->add($items);

echo "items=" . $items . "\n";
echo "total=" . $total . "\n";

shared state helper Trait methods are useful when several classes need the same small state update.