The Fast, Secure and Professional PHP Framework. Yii is a high-performance PHP framework best for developing Web 2.0 applications. Yii comes with rich features: MVC, DAO/ActiveRecord, I18N/L10N, caching, authentication and role-based access control, scaffolding, testing, etc. It can reduce your development time significantly.

Yii is an open source, object-oriented, component-based MVC PHP web application framework. Yii is pronounced as "Yee" or in Chinese it means "simple and evolutionary" and it can be an acronym for "Yes It is!

Yii is a free, open-source Web application development framework written in PHP5 that promotes clean, DRY design and encourages rapid development. It works to streamline your application development and helps to ensure an extremely efficient, extensible, and maintainable end product.

Model-View-Controller (MVC) design pattern

Yii adopts the proven MVC architecture, which allows for clean separation of concerns (SoC).

Database Access Objects (DAO), Query Builder, Active Record, DB Migration

Yii allows developers to model database data in terms of objects and avoid the tedium and complexity of writing repetitive SQL statements.

Form input and validation

Yii makes collecting form input extremely easy and safe. It comes with a set of validators as well as numerous helper methods and widgets to simplify the task for form input and validation.

AJAX-enabled widgets

Integrated with jQuery, Yii comes with a set of AJAX-enabled widgets, such as autocomplete input field, treeview, data grid, which enables writing highly efficient and versatile user interface extremely simple.

Authentication and authorization

Yii has built-in authentication support. It also supports authorization via hierarchical role-based access control (RBAC).

Skinning and theming

Yii implements a skinning and theming mechanism that allows you to quickly switch the outlook of a Yii-power website.

Web services

Yii supports automatic generation of complex WSDL service specifications and management of Web service request handling.

Internationalization (I18N) and localization (L10N)

Yii supports message translation, date and time formatting, number formatting, and interface localization.

Layered caching scheme

Yii supports data caching, page caching, fragment caching and dynamic content. The storage medium of caching can be changed easily without touching the application code.

Error handling and logging

Errors are handled and presented more nicely, and log messages can be categorized, filtered and routed to different destinations.

Security

Yii is equipped with many security measures to help prevent your Web applications from attacks such as SQL injection, cross-site scripting (XSS), cross-site request forgery (CSRF), and cookie tampering.

Unit and functionality testing

Yii provides support for writing and running unit tests as well as functionality tests, based on PHPUnit and Selenium.

Automatic code generation

Yii provides a set of intuitive and highly extensible code generation tools that can help you quickly generate the code you need for features such as form input, CRUD.

Friendly with third-party code

Yii is carefully designed to work well with third-party code. For example, you can use code from PEAR or Zend Framework in your Yii application.

Detailed documentation

Every single method or property is clearly documented. A book and comprehensive tutorials are also available for you to systematically learn Yii.

Extension library

Yii provides an extension library consisting of user-contributed components. This makes the above feature list never ending.

Yii is a high-performance framework. The graph below shows how efficient Yii is when compared with other popular PHP frameworks. In the graph, RPS stands for "request per second" which describes how many requests an application written in a framework can process per second. The higher the number, the more efficient a framework is. As we can see that Yii outperforms all other frameworks in this comparison. The performance advantage of Yii is especially significant when the widely used APC extension is enabled.

Performance alone is not the whole story (otherwise we should all use plain HTML or PHP). With such superior performance, Yii still provides a very rich feature set which can greatly improve your development efficiency.

Yii is so much faster because it is using the lazy loading technique extensively. For example, it does not include a class file until the class is used for the first time; and it does not create an object until the object is accessed for the first time. Other frameworks suffer from the performance hit because they would enable a functionality (e.g. DB connection, user session) no matter it is used or not during a request.

Below we explain how we design the benchmark applications and obtain the above RPS figures.

Since our goal is to compare the minimal overhead of each framework, the benchmark application for each framework should be the simplest one. We choose to display a "Hello World" text string by placing an echo statement in the default action of each application. Any additional framework features (e.g. session) are disabled to ensure fairness of the comparison. To obtain a copy of the benchmark applications, please check out the phpmark project.

We choose to do "Hello World" testing mainly to achieve our goal, i.e., to find out the minimal overhead of each framework. Many people complain that the "Hello World" application is meaningless because a real-world application often needs to deal with more complex tasks, such as database queries. This is not very true. In reality, especially in a large-scale Web 2.0 application, we often encounter scenarios that are very close to "Hello World". For example, an application may need to respond to an AJAX request that should return the current server timestamp; a page has a large portion of its content being cached and an application just needs to fetch the cached content and display it.

Another reason for "Hello World" is because when more complex features (e.g. database queries) are involved, it becomes a very difficult task to ensure the comparison is fair. For example, one framework could be very efficient at performing database queries, but it lacks caching scheme; while another framework is a bit slower with database queries, but it has sophisticated caching feature to help ease the performance hit. There are simply too many factors involved to conduct a fair comparison.

The RPS numbers were obtained using the Apache Bench tool with the command "ab -t 30 -c 10 URL" (i.e., at concurrency level 10 running the test for 30 seconds). To get the number for each framework, we first stop and then start the Apache Web server to avoid interference. We also run the test application for a few times to "warm up" the testing environment. In the phpmark project, we have a shell script named benchmark.sh to automate the benchmarking procedure.

The testing environment is as follows:

• Operating System: Red Hat Enterprise Linux Server release 5.2
• Web Server: Apache httpd 2.0.40
• PHP: 5.2.6, any non-essential extensions are disabled
• CPU: Dual Intel Xeon 3.2GHz
• Main Memory: 2GB
• Hard Drive: 73GB 15K RPM SCSI/SAS HDD
• The APC ini settings are as follows:
• apc.enabled=1
• apc.shm_segments=1
• apc.optimization=0
• apc.shm_size=32
• apc.ttl=7200
• apc.user_ttl=7200
• apc.num_files_hint=1024
• apc.mmap_file_mask=/tmp/apc.XXXXXX
• apc.enable_cli=1
• apc.cache_by_default=1
• apc.stat=0

Yii is an open source project released under the terms of the BSD License. This means that you can use Yii for free to develop either open-source or proprietary Web applications.

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The Definitive Guide to Yii is the most comprehensive Yii documentation that gives the definitive description of every feature of Yii. It is being constantly updated to reflect the latest enhancements and changes. A PDF version of this tutorial can be found in the Yii releases.

Tutorial Guide