AppExtension-function.php

<?php

namespace App\Twig;

use Twig\Extension\AbstractExtension;
use Twig\TwigFunction;

class AppExtension extends AbstractExtension
{
    public function getFunctions()
    {
        return [
            new TwigFunction('area', [$this, 'calculateArea']),
        ];
    }

    public function calculateArea(int $width, int $length)
    {
        return $width * $length;
    }
}

AppExtension.php

<?php

namespace App\Twig;

use Twig\Extension\AbstractExtension;
use Twig\TwigFilter;

class AppExtension extends AbstractExtension
{
    public function getFilters()
    {
        return [
            new TwigFilter('price', [$this, 'formatPrice']),
        ];
    }

    public function formatPrice($number, $decimals = 0, $decPoint = '.', $thousandsSep = ',')
    {
        $price = number_format($number, $decimals, $decPoint, $thousandsSep);
        $price = '$'.$price;

        return $price;
    }
}