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docs/guide/start-databases.md
......@@ -46,7 +46,7 @@ INSERT INTO `Country` VALUES ('US','United States',278357000);
At this point, you have a database named `yii2basic`, and within it a `country` table with three columns, containing ten rows of data.
Configuring the DB Connection <a name="configuring-db-connection"></a>
Configuring a DB Connection <a name="configuring-db-connection"></a>
---------------------------
Before proceeding, make sure you have installed both the [PDO](http://www.php.net/manual/en/book.pdo.php) PHP extension and
......@@ -129,10 +129,10 @@ You may find more detailed information in the [Active Record](db-active-record.m
Creating an Action <a name="creating-action"></a>
------------------
To expose the country data to end users, you need to create a new action. Instead of doing this in the `site`
controller like you did in the previous sections, it makes more sense to create a new controller specifically
for all actions about manipulating country data. Name this new controller as `CountryController` and create
an `index` action in it, as shown in the following,
To expose the country data to end users, you need to create a new action. Instead of placing the new action in the `site`
controller, like you did in the previous sections, it makes more sense to create a new controller specifically
for all actions related to the country data. Name this new controller `CountryController`, and create
an `index` action in it, as shown in the following.
```php
<?php
......@@ -169,25 +169,25 @@ class CountryController extends Controller
Save the above code in the file `controllers/CountryController.php`.
The `index` action calls `Country::find()` to build a DB query and retrieve all data from the `country` table.
The `index` action calls `Country::find()`. This Active Record method builds a DB query and retrieves all of the data from the `country` table.
To limit the number of countries returned in each request, the query is paginated with the help of a
[[yii\data\Pagination]] object. The `Pagination` object serves for two purposes:
[[yii\data\Pagination]] object. The `Pagination` object serves two purposes:
* Sets the `offset` and `limit` clauses for the SQL statement represented by the query so that it only
returns a single page of data (at most 5 rows in a page).
* Being used in the view to display a pager consisting of a list of page buttons, as will be explained in
returns a single page of data at a time (at most 5 rows in a page).
* It's used in the view to display a pager consisting of a list of page buttons, as will be explained in
the next subsection.
At the end, the `index` action renders a view named `index` and passes the country data as well as the pagination
At the end of the code, the `index` action renders a view named `index`, and passes the country data as well as the pagination
information to it.
Creating a View <a name="creating-view"></a>
---------------
Under the `views` directory, first create a sub-directory named `country`. This will used to hold all
Under the `views` directory, first create a sub-directory named `country`. This folder will used to hold all the
views rendered by the `country` controller. Within the `views/country` directory, create a file named `index.php`
with the following content:
containing the following:
```php
<?php
......@@ -207,7 +207,7 @@ use yii\widgets\LinkPager;
<?= LinkPager::widget(['pagination' => $pagination]) ?>
```
The view consists of two parts. In the first part, the country data is traversed and rendered as an unordered HTML list.
The view has two sections relative to displaying the country data. In the first part, the provided country data is traversed and rendered as an unordered HTML list.
In the second part, a [[yii\widgets\LinkPager]] widget is rendered using the pagination information passed from the action.
The `LinkPager` widget displays a list of page buttons. Clicking on any of them will refresh the country data
in the corresponding page.
......@@ -216,7 +216,7 @@ in the corresponding page.
Trying it Out <a name="trying-it-out"></a>
-------------
To see how it works, use your browser to access the following URL:
To see how all of the above code works, use your browser to access the following URL:
```
http://hostname/index.php?r=country/index
......@@ -224,34 +224,34 @@ http://hostname/index.php?r=country/index
![Country List](images/start-country-list.png)
You will see a page showing five countries. And below the countries, you will see a pager with four buttons.
If you click on the button "2", you will see that the page displays another five countries in the database.
Observe more carefully and you will find the URL in the browser changes to
At first, you will see a page showing five countries. Below the countries, you will see a pager with four buttons.
If you click on the button "2", you will see the page display another five countries in the database: the second page of records.
Observe more carefully and you will find that the URL in the browser also changes to
```
http://hostname/index.php?r=country/index&page=2
```
Behind the scene, [[yii\data\Pagination|Pagination]] is playing the magic.
Behind the scenes, [[yii\data\Pagination|Pagination]] is providing all of the ncessary functionality to paginate a data set:
* Initially, [[yii\data\Pagination|Pagination]] represents the first page, which sets the country query
* Initially, [[yii\data\Pagination|Pagination]] represents the first page, which reflects the country SELECT query
with the clause `LIMIT 5 OFFSET 0`. As a result, the first five countries will be fetched and displayed.
* The [[yii\widgets\LinkPager|LinkPager]] widget renders the page buttons using the URLs
created by [[yii\data\Pagination::createUrl()|Pagination]]. The URLs will contain the query parameter `page`
representing different page numbers.
created by [[yii\data\Pagination::createUrl()|Pagination]]. The URLs will contain the query parameter `page`, which
represents the different page numbers.
* If you click the page button "2", a new request for the route `country/index` will be triggered and handled.
[[yii\data\Pagination|Pagination]] reads the `page` query parameter and sets the current page number 2.
The new country query will thus have the clause `LIMIT 5 OFFSET 5` and return back the next five countries
[[yii\data\Pagination|Pagination]] reads the `page` query parameter from the URL and sets the current page number to 2.
The new country query will thus have the clause `LIMIT 5 OFFSET 5` and return the next five countries
for display.
Summary <a name="summary"></a>
-------
In this section, you have learned how to work with a database. You have also learned how to fetch and display
In this section, you learned how to work with a database. You also learned how to fetch and display
data in pages with the help of [[yii\data\Pagination]] and [[yii\widgets\LinkPager]].
In the next section, you will learn how to use the powerful code generation tool, called [Gii](tool-gii.md),
to help you rapidly implement some commonly required features, such as the Create-Read-Update-Delete (CRUD)
operations about the data in a DB table. As a matter of fact, the code you have just written can all
be automatically generated using this tool.
operations for working with the data in a database table. As a matter of fact, the code you have just written can all
be automatically generated in Yii using the Gii tool.
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