Libraries

Helpers are small function collections; libraries are classes; services create shared objects. Choosing the right one keeps repeated work out of controllers and views.

Built-in helpers

The URL helper provides base_url(), site_url(), and route_to(). The form helper builds fields and labels. The HTML helper escapes and formats output, and the security helper exposes CSRF tokens.

helper('url');
echo base_url('assets/css/app.css');

helper(['form', 'url']);
echo form_open('/contact');

Write a custom helper

<?php // app/Helpers/price_helper.php

if (! function_exists('format_price')) {
    function format_price(float $amount): string
    {
        return '$' . number_format($amount, 2);
    }
}

helper('price');
echo format_price(49.5);

Guard helper functions with function_exists() so they cannot be declared twice.

Libraries

A library encapsulates a feature such as an invoice calculator or an API client. Place it in app/Libraries under the App\Libraries namespace.

<?php

namespace App\Libraries;

class InvoiceTotals
{
    public function withTax(float $subtotal, float $rate): float
    {
        return round($subtotal * (1 + $rate), 2);
    }
}

$totals = new \App\Libraries\InvoiceTotals();
$total  = $totals->withTax(200.0, 0.18);

Services

Services give you a central way to create and reuse objects. The framework's own services are available through service().

$request = service('request');
$session = service('session');
$logger  = service('logger');

Third-party packages

Install Composer packages as usual and use their namespaces directly. Keep package-specific code behind a small library or service so the rest of the application does not depend on the package API.

Use a helper for one pure function, a library for stateful behaviour, and a service when the object should be shared across the request.