# URL
The URL view helper is used to create a string representation of the routes that
you define within your application. The syntax for the view helper is
`$this->url($name, $params, $options, $reuseMatchedParameters)`, using the
following definitions for the helper arguments:
- `$name`: The name of the route you want to output.
- `$params`: An array of parameters that is defined within the respective route
configuration.
- `$options`: An array of options that will be used to create the URL.
- `$reuseMatchedParams`: A flag indicating if the currently matched route
parameters should be used when generating the new URL.
Let's take a look at how this view helper is used in real-world applications.
## Basic Usage
The following example shows a simple configuration for a news module. The route
is called `news` and it has two **optional** parameters called `action` and
`id`.
```php
// In a configuration array (e.g. returned by some module's module.config.php)
'router' => [
'routes' => [
'news' => [
'type' => 'segment',
'options' => [
'route' => '/news[/:action][/:id]',
'constraints' => [
'action' => '[a-zA-Z][a-zA-Z0-9_-]*',
],
'defaults' => [
'controller' => 'news',
'action' => 'index',
],
],
],
],
],
```
First, let's use the view helper to create the output for the URL `/news` without any of the
optional parameters being used:
```php
<a href="<?= $this->url('news'); ?>">News Index</a>
```
This will render the output:
```html
<a href="/news">News Index</a>
```
Now let's assume we want to get a link to display the detail page of a single
news entry. For this task, the optional parameters `action` and `id` need to
have values assigned. This is how you do that:
```php
<a href="<?= $this->url('news', ['action' => 'details', 'id' => 42]); ?>">
Details of News #42
</a>
```
This will render the output:
```html
<a href="/news/details/42">News Index</a>
```
## Query String Arguments
Most SEO experts agree that pagination parameters should not be part of the URL
path; for example, the following URL would be considered a bad practice:
`/news/archive/page/13`. Pagination is more correctly accomplished using a query
string arguments, such as `/news/archive?page=13`. To achieve this, you'll need
to make use of the `$options` argument from the view helper.
We will use the same route configuration as defined above:
```php
// In a configuration array (e.g. returned by some module's module.config.php)
'router' => [
'routes' => [
'news' => [
'type' => 'segment',
'options' => [
'route' => '/news[/:action][/:id]',
'constraints' => [
'action' => '[a-zA-Z][a-zA-Z0-9_-]*',
],
'defaults' => [
'controller' => 'news',
'action' => 'index',
],
],
],
],
],
```
To generate query string arguments from the view helper, you need to assign them
as the third argument using the `query` key like this:
```php
<?php
$url = $this->url(
'news',
['action' => 'archive'],
[
'query' => [
'page' => 13,
],
]
);
?>
<a href="<?= $url; ?>">News Archive Page #13</a>
```
The above code sample would output:
```html
<a href="/news/archive?page=13">News Archive Page #13</a>
```
## Fragments
Another possible entry within the `$options` array is the assignment of URL
fragments (typically used to link to in-page anchors), denoted with using the
`fragment` key. Let's assume we want to enter a link for users to directly jump
to the comment section of a details page:
```php
<?php
$url = $this->url(
'news',
['action' => 'details', 'id' => 42],
[
'fragment' => 'comments',
]
);
?>
<a href="<?= $url; ?>">Comment Section of News #42</a>
```
The above code sample would output:
```html
<a href="/news/details/42#comments">Comment Section of News #42</a>
```
You can use `fragment` and `query` options at the same time!
```php
<?php
$url = $this->url(
'news',
['action' => 'details', 'id' => 42],
[
'query' => [
'commentPage' => 3,
],
'fragment' => 'comments',
]
);
?>
<a href="<?= $url; ?>">Comment Section of News #42</a>
```
The above code sample would output:
```html
<a href="/news/details/42?commentPage=3#comments">Comment Section of News #42</a>
```
## Fully Qualified Domain Name
Another possible entry within the `$options` array is to output a fully
qualified domain name (absolute URL), denoted using the `force_canonical` key:
```php
<?php
$url = $this->url(
'news',
[],
[
'force_canonical' => true,
]
);
?>
<a href="<?= $url; ?>">News Index</a>
```
The above code sample would output:
```html
<a href="http://www.example.com/news">News Index</a>
```
## Reusing Matched Parameters
When you're on a route that has many parameters, often times it makes sense to
reuse currently matched parameters instead of assigning them explicitly. In this
case, the argument `$reuseMatchedParams` will come in handy.
As an example, we will imagine being on a detail page for our `news` route. We
want to display links to the `edit` and `delete` actions without having to
assign the ID again:
```php
// Currently url /news/details/777
<a href="<?= $this->url('news', ['action' => 'edit'], null, true); ?>">Edit Me</a>
<a href="<?= $this->url('news', ['action' => 'delete'], null, true); ?>">Delete Me</a>
```
Notice the `true` argument in the fourth position. This tells the view helper to
use the matched `id` (`777`) when creating the new URL:
```html
<a href="/news/edit/777">Edit Me</a>
<a href="/news/delete/777">Edit Me</a>
```
### Shorthand
Due to the fact that reusing parameters is a use case that can happen when no
route options are set, the third argument for the URL view helper will be
checked against its type; when a `boolean` is passed, the helper uses it to set
the value of the `$reuseMatchedParams` flag:
```php
$this->url('news', ['action' => 'archive'], null, true);
// is equal to
$this->url('news', ['action' => 'archive'], true);
```