Mastering Yii: Advance your modern web application development skills with Yii Framework 2

There are several different ways to install Yii2, ranging from downloading the framework from source control (typically, from GitHub at https://github.com/yiisoft/yii2) to using a package manager such as Composer. With modern web applications, Composer is the preferred method to install Yii2 as it enables us to install, update, and manage all dependencies and extensions for our application in an automated fashion. Additionally, using Composer, we can ensure that Yii Framework 2 is kept up to date with the latest security and bug fixes. Composer can be installed by following the instructions on https://getcomposer.org. Typically, this process looks as follows:

curl -sS https://getcomposer.org/installer | php

Alternatively, if you don't have cURL available on your system, it can be installed through PHP itself:

php -r "readfile('https://getcomposer.org/installer');" | php

Once installed, we should move Composer to a more centralized directory so that we can call it from any directory on our system. Installing Composer from a centralized directory rather than on a per-project basis has several advantages:

A good directory to move Composer to is /usr/local/bin, as shown in the following example:

mv composer.phar /usr/local/bin/composer
chmod a+x /usr/local/bin/composer

Alternatively, if you have Composer installed on your system already, ensure that you update it to the latest version by running this:

composer self-update

Once Composer is installed, we'll need to install a global plugin called The Composer Asset Plugin (available at https://github.com/francoispluchino/composer-asset-plugin). This plugin enables Composer to manage asset files for us without the need to install additional software (these programs are Bower, an asset dependency manager created by Twitter, and Node Package Manager, or NPM, which is a JavaScript dependency manager).

composer global require "fxp/composer-asset-plugin:1.0.0"

With Composer installed, we can now instantiate our application. If we want to install an existing Yii2 package, we can simply run the following:

composer create-project --prefer-dist <package/name> <foldername>

Using the Yii2 basic app as an example, this command will look like this:

composer create-project --prefer-dist yiisoft/yii2-app-basic basic

After running the command, you should see output similar to the following:

Installing yiisoft/yii2-app-basic (2.0.6)
  - Installing yiisoft/yii2-app-basic (2.0.6)
    Downloading: 100%
Created project in basic
Loading composer repositories with package information
Installing dependencies (including require-dev)
  - Installing yiisoft/yii2-composer (2.0.3)
  - Installing ezyang/htmlpurifier (v4.6.0)
  - Installing bower-asset/jquery (2.1.4)
  - Installing bower-asset/yii2-pjax (v2.0.4)
  - Installing bower-asset/punycode (v1.3.2)
  - Installing bower-asset/jquery.inputmask (3.1.63)
  - Installing cebe/markdown (1.1.0)
  - Installing yiisoft/yii2 (2.0.6)
  - Installing swiftmailer/swiftmailer (v5.4.1)
  - Installing yiisoft/yii2-swiftmailer (2.0.4)
  - Installing yiisoft/yii2-codeception (2.0.4)
  - Installing bower-asset/bootstrap (v3.3.5)
  - Installing yiisoft/yii2-bootstrap (2.0.5)
  - Installing yiisoft/yii2-debug (2.0.5)
  - Installing bower-asset/typeahead.js (v0.10.5)
  - Installing phpspec/php-diff (v1.0.2)
  - Installing yiisoft/yii2-gii (2.0.4)
  - Installing fzaninotto/faker (v1.5.0)
  - Installing yiisoft/yii2-faker (2.0.3)
Writing lock file
Generating autoload files
> yii\composer\Installer::postCreateProject
chmod('runtime', 0777)...done.
chmod('web/assets', 0777)...done.
chmod('yii', 0755)...done.

This command will install the Yii2 basic app to a folder called basic. When creating a new Yii2 project, you'll typically want to use the create-project command to clone "yii2-app-basic" and then develop your application from there as the basic app comes prepopulated with just about everything you need to start a new project. However, you can also create a Yii2 project from scratch that, while more complicated, gives you more control over your application's structure.

Let's take a look at the composer.json file that was created when we ran the create-project command:

{
    "name": "yiisoft/yii2-app-basic",
    "description": "Yii 2 Basic Application Template",
    "keywords": ["yii2", "framework", "basic", "application template"],
    "homepage": "http://www.yiiframework.com/",
    "type": "project",
    "license": "BSD-3-Clause",
    "support": {
        "issues": "https://github.com/yiisoft/yii2/issues?state=open",
        "forum": "http://www.yiiframework.com/forum/",
        "wiki": "http://www.yiiframework.com/wiki/",
        "irc": "irc://irc.freenode.net/yii",
        "source": "https://github.com/yiisoft/yii2"
    },
    "minimum-stability": "stable",
    "require": {
        "php": ">=5.4.0",
        "yiisoft/yii2": "*",
        "yiisoft/yii2-bootstrap": "*",
        "yiisoft/yii2-swiftmailer": "*"
    },
    "require-dev": {
        "yiisoft/yii2-codeception": "*",
        "yiisoft/yii2-debug": "*",
        "yiisoft/yii2-gii": "*",
        "yiisoft/yii2-faker": "*"
    },
    "config": {
        "process-timeout": 1800
    },
    "scripts": {
        "post-create-project-cmd": [
            "yii\\composer\\Installer::postCreateProject"
        ]
    },
    "extra": {
        "yii\\composer\\Installer::postCreateProject": {
            "setPermission": [
                {
                    "runtime": "0777",
                    "web/assets": "0777",
                    "yii": "0755"
                }
            ],
            "generateCookieValidationKey": [
                "config/web.php"
            ]
        },
        "asset-installer-paths": {
            "npm-asset-library": "vendor/npm",
            "bower-asset-library": "vendor/bower"
        }
    }
}

While most of these items (such as the name, description, license, and require blocks) are rather self-explanatory, there are a few Yii2-specific items in here that we should take note of. The first section we want to look at is the "scripts" section:

"scripts": {
    "post-create-project-cmd": [
        "yii\\composer\\Installer::postCreateProject"
    ]
}

This script tells Composer that when the create-project command is run, it should run the postCreateProject static function. Looking at the the framework source code, we see that this file is referenced in the yii2-composer package (refer to https://github.com/yiisoft/yii2-composer/blob/master/Installer.php#L232). This command then runs several post-project creation actions, namely setting the local disk permissions, generating a unique cookie validation key, and setting some asset installer paths for composer-asset-plugin.

Next, we have the "extra" block:

"extra": {
    "yii\\composer\\Installer::postCreateProject": {
        "setPermission": [
            {
                "runtime": "0777",
                "web/assets": "0777",
                "yii": "0755"
            }
        ],
        "generateCookieValidationKey": [
            "config/web.php"
        ]
    },
    "asset-installer-paths": {
        "npm-asset-library": "vendor/npm",
        "bower-asset-library": "vendor/bower"
    }
}

This section tells Composer to use these options when it runs the postCreateProject command. These preconfigured options give us a good starting point to create our applications.

With our basic application now installed, let's take a look at a few basic configuration and bootstrap files that Yii2 automatically generated for us.

php requirements.php

Yii Application Requirement Checker
This script checks if your server configuration meets the requirements for running Yii application.
It checks if the server is running the right version of PHP,  if appropriate PHP extensions have been loaded, and if php.ini file settings are correct.
Check conclusion:
-----------------
PHP version: OK
[... more checks here ...]
-----------------------------------------
Errors: 0   Warnings: 6   Total checks: 21

<?php

// comment out the following two lines when deployed to production
defined('YII_DEBUG') or define('YII_DEBUG', true);
defined('YII_ENV') or define('YII_ENV', 'dev');

require(__DIR__ . '/../vendor/autoload.php');
require(__DIR__ . '/../vendor/yiisoft/yii2/Yii.php');

$config = require(__DIR__ . '/../config/web.php');

(new yii\web\Application($config))->run();

<?php

return [
    'class' => 'yii\db\Connection',
    'dsn' => 'mysql:host=localhost;dbname=yii2basic',
    'username' => 'root',
    'password' => '',
    'charset' => 'utf8',
];

<?php return require __DIR__ . '/env/' . APPLICATION_ENV . '/db.php';

<?php return require __DIR__ . '/env/' . APPLICATION_ENV . '/params.php';

<?php return require __DIR__ . '/env/' . APPLICATION_ENV . '/env.php';

cp –R config/env/dev config/env/test
cp –R config/env/dev config/env/uat
cp –R config/env/dev config/env/prod

location ~ \.php$ {
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;
        fastcgi_pass   127.0.0.1:9000;
        #fastcgi_pass unix:/var/run/php5-fpm.sock;
        try_files $uri =404;
    }

fastcgi_param   APPLICATION_ENV "dev";

# Set document root to be "basic/web"
DocumentRoot "path/to/basic/web"

<Directory "path/to/basic/web">
    # use mod_rewrite for pretty URL support
    RewriteEngine on
    # If a directory or a file exists, use the request directly
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    # Otherwise forward the request to index.php
    RewriteRule . index.php

    # ...other settings...
</Directory>

SetEnv   APPLICATION_ENV dev

There are two base classes that almost everything in Yii2 extends from: the Component class and the Object class.

Yii::$app->componentID

Yii::$app->db

Yii::$app->cache

<?php return [
    'bootstrap' => [
        'log'
    ],
    […]
]

In Yii2, path aliases are used to represent file paths or URL paths so that we don't hardcode paths or URLs directly into our application. In Yii2, aliases always start with the @ symbol so that Yii knows how to differentiate it from a file path or URL.

Aliases can be defined in several ways. The most basic way to define a new alias is to call \Yii::setAlias():

\Yii::setAlias('@path', '/path/to/example');
\Yii::setAlias('@example, 'https://www.example.com');

Aliases can also be defined in the application configuration file by setting the alias option as follows:

return [
    // ...
    'aliases' => [
        '@path => '/path/to/example,
        '@example' => 'https://www.example.com',
    ],
];

Also, aliases can be easily retrieved using \Yii::getAlias():

\Yii::getAlias('@path') // returns /path/to/example
\Yii::getAlias('@example') // returns https://www.example.com

Several places in Yii are alias-aware and will accept aliases as inputs. For example, yii\caching\FileCache accepts a file alias as an alias for the $cachePath parameter:

$cache = new FileCache([
    'cachePath' => '@runtime/cache',
]);

In this chapter, we went over how to create new Yii2 applications via composer. We also went over the basic configuration files that come with Yii2 as well as how to configure our web application to load environment-specific configuration files. Finally, we also covered components, objects, and path aliases, which are fundamental to gaining mastery over Yii.

In the next chapter, we'll cover everything you need to know in order to become a master of console commands and applications.