Yii: a component-based MVC framework for PHP

It relies on a single official source: the Yii 2.0 guide introduction page.

What Yii is

Yii is a framework, not a runtime and not a CMS. The source describes it as a high performance, component-based PHP framework for rapidly developing modern Web applications. It runs on top of PHP, so PHP core (the language, its extensions and the engine that executes scripts) stays a separate layer. Yii adds structure, reusable components and conventions.

The distinction from a CMS matters. A CMS product such as Drupal ships content types, an administration interface and a ready-made site model. A framework provides building blocks for you to assemble into your own application. The source says Yii suits large applications such as portals, forums, content management systems, e-commerce projects and RESTful web services. That means you could build a CMS with it, but Yii itself is not one.

Yii versions

The page says Yii has two major versions available, 1.1 and 2.0. Version 1.1 is described as the old generation, in maintenance mode. Version 2.0 is described as a complete rewrite built on Composer, PSR, namespaces and traits, and as the current generation. The guide is mainly about 2.0.

The page's version selector also lists Yii3, but the supplied text does not describe Yii3. Its architecture, requirements, PHP compatibility and relationship to Yii 2 are unknown from this evidence. Treat Yii 2 and Yii 3 as separate products with separate guides and verify which one you are reading. Because of this gap, and because no support dates were supplied, the lifecycle is recorded as unknown.

Architecture and content model

The source states that Yii implements the MVC (Model-View-Controller) pattern and promotes code organization around it. It also says Yii prefers simple, elegant code over strict adherence to design patterns, is full-stack and is extensible. Listed features include:

• Query builders and ActiveRecord for relational and NoSQL databases.
• RESTful API support.
• Multi-tier caching.
• An extension architecture for redistributable packages.

The navigation lists topics such as entry scripts, applications, application components, controllers, models, views, modules, filters, widgets, assets and extensions. The text of those pages was not supplied, so this guide only names them as the documented map of the framework.

Execution model

The supplied page does not explain how a request is executed. The navigation mentions entry scripts and request handling, which suggests a conventional entry-point model, but this is an inference from headings, not documented behavior.

In a classic request lifetime, PHP starts for each request, the application is built, a response is sent and nearly all in-process state is discarded. A persistent worker keeps the process alive and handles many requests in one memory space. The source says nothing about Yii running in persistent workers, so that support is unknown.

Runtimes and extensions are separate projects with their own documentation. Swoole and Open Swoole are two distinct projects, and neither is part of Yii. Async libraries and framework adapters are not standalone PHP runtimes either. If you ever run any application in a persistent worker, plan for state leakage:

• Static properties and singletons can carry one user's data into the next request.
• Container or service instances can keep request-specific objects such as the current user, locale or database transaction.
• Open connections, buffers, caches and temporary files can persist unexpectedly.

Cleanup means resetting or recreating request-scoped objects at the end of each request, avoiding mutable global state and recycling workers on a schedule. Verify that behavior against the documentation of whatever worker tool you choose. This guide cannot confirm it for Yii.

Practical use cases

Based on the source, Yii fits full-stack web applications, portals, forums, e-commerce, RESTful web services and custom content management systems. If you want a finished CMS with an editorial interface, evaluate a CMS product instead and keep the two categories separate.

Installation approach

The source states that Yii 2.0 requires PHP 7.4.0 or above and runs best with the latest PHP version. It also says each Yii release includes a requirement checker for feature-specific needs. The Installing Yii page is only named in the navigation, so this guide supplies no Composer package names or install commands for Yii. Follow the official installation page for the version you choose.

This site's learning track uses PHP 8.4, with PHP 8.5 planned. The source gives only a minimum of 7.4.0, so Yii 2 compatibility with PHP 8.4 or 8.5 is unknown here. Confirm it in the official release information before relying on it.

The example below is a small preflight script. It is not Yii code. It checks that your PHP meets the documented minimum and reports whether a Composer autoloader exists beside it.

Strengths

According to the source:

• Component-based architecture and a full-stack feature set.
• Caching support and query builders.
• Extensibility, with nearly every core piece customizable or replaceable.
• Stated high performance as a primary goal. This guide makes no benchmark claims.
• A core team and a large community.

Limitations

• Requires solid object-oriented PHP knowledge, including namespaces and traits.
• Yii 2 and Yii 3 differ, and the supplied evidence covers only Yii 2.
• Yii 1.1 is in maintenance mode according to the source, so it should not be chosen for new work.
• The source gives no license, current version number, support timeline, PHP 8.4 or 8.5 compatibility, or persistent-worker guidance. All of these are unknown here.

Deployment

The navigation lists Docker, shared hosting and performance tuning topics, but their contents were not supplied. This guide therefore gives no deployment recipe. In general, keep any development server bound to 127.0.0.1, and never expose FastCGI publicly. Use the official Yii pages for production guidance.

Links

Use the official Yii 2.0 guide introduction, which is the only source for this guide. Runtime PHP examples may need Composer and network services, so they are not browser exercises.

<?php

declare(strict_types=1);

// Minimum PHP version documented for Yii 2.0 in the official guide introduction.
const DOCUMENTED_YII2_MINIMUM = '7.4.0';

$meetsMinimum = version_compare(PHP_VERSION, DOCUMENTED_YII2_MINIMUM, '>=');
$autoloadPath = __DIR__ . '/vendor/autoload.php';

echo 'PHP version: ' . PHP_VERSION . PHP_EOL;
echo 'SAPI: ' . PHP_SAPI . PHP_EOL;
echo 'Documented Yii 2.0 minimum: ' . DOCUMENTED_YII2_MINIMUM . PHP_EOL;
echo 'Meets documented minimum: ' . ($meetsMinimum ? 'yes' : 'no') . PHP_EOL;
echo 'Composer autoloader present: ' . (is_file($autoloadPath) ? 'yes' : 'no') . PHP_EOL;
echo 'Note: PHP 8.4 compatibility of Yii 2 is not stated in the source; check official release information.' . PHP_EOL;

exit($meetsMinimum ? 0 : 1);

cd yii-preflight
php --version
php preflight.php