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Introduction - Zend_View
Zend_View is a class for working with the "view" portion of the model-view-controller pattern. That is, it exists to help keep the view script separate from the model and controller scripts. It provides a system of helpers, output filters, and variable escaping.
Zend_View is template system agnostic; you may use PHP as your template language, or create instances of other template systems and manipulate them within your view script.
Essentially, using Zend_View happens in two major steps: 1. Your controller script creates an instance of Zend_View and assigns variables to that instance. 2. The controller tells the Zend_View to render a particular view, thereby handing control over the view script, which generates the view output.
As a simple example, let us say your controller has a list of book data that it wants to have rendered by a view. The controller script might look something like this:
- // use a model to get the data for book authors and titles.
- $data = array(
- 'author' => 'Hernando de Soto',
- 'title' => 'The Mystery of Capitalism'
- 'author' => 'Henry Hazlitt',
- 'title' => 'Economics in One Lesson'
- 'author' => 'Milton Friedman',
- 'title' => 'Free to Choose'
- // now assign the book data to a Zend_View instance
- $view = new Zend_View();
- $view->books = $data;
- // and render a view script called "booklist.php"
- echo $view->render('booklist.php');
Now we need the associated view script, "booklist.php". This is a PHP script like any other, with one exception: it executes inside the scope of the Zend_View instance, which means that references to $this point to the Zend_View instance properties and methods. (Variables assigned to the instance by the controller are public properties of the Zend_View instance). Thus, a very basic view script could look like this:
- if ($this->books): ?>
- <!-- A table of some books. -->
- <?php foreach ($this->books as $key => $val): ?>
- <td><?php echo $this->escape($val['author']) ?></td>
- <td><?php echo $this->escape($val['title']) ?></td>
- <?php endforeach; ?>
- <?php else: ?>
- <p>There are no books to display.</p>
- <?php endif;?>
Note how we use the "escape()" method to apply output escaping to variables.
Zend_View has several options that may be set to configure the behaviour of your view scripts.
basePath: indicate a base path from which to set the script, helper, and filter path. It assumes a directory structure of:
This may be set via setBasePath(), addBasePath(), or the basePath option to the constructor.
encoding: indicate the character encoding to use with htmlentities(), htmlspecialchars(), and other operations. Defaults to UTF-8. May be set via setEncoding() or the encoding option to the constructor.
escape: indicate a callback to be used by escape(). May be set via setEscape() or the escape option to the constructor.
filter: indicate a filter to use after rendering a view script. May be set via setFilter(), addFilter(), or the filter option to the constructor.
strictVars: force Zend_View to emit notices and warnings when uninitialized view variables are accessed. This may be set by calling strictVars(true) or passing the strictVars option to the constructor.
Short Tags with View Scripts
In our examples, we make use of PHP long tags: <?php. We also favor the use of » alternate syntax for control structures. These are convenient shorthands to use when writing view scripts, as they make the constructs more terse, keep statements on single lines, and eliminate the need to hunt for brackets within HTML.
In previous versions, we often recommended using short tags (<? and <?=), as they make the view scripts slightly less verbose. However, the default for the php.ini short_open_tag setting is typically off in production or on shared hosts -- making their use not terribly portable. If you use template XML in view scripts, short open tags will cause the templates to fail validation. Finally, if you use short tags when short_open_tag is off, the view scripts will either cause errors or simply echo PHP code back to the viewer.
If, despite these warnings, you wish to use short tags but they are disabled, you have two options:
Turn on short tags in your .htaccess file:
- php_value "short_open_tag" "on"
This will only be possible if you are allowed to create and utilize .htaccess files. This directive can also be added to your httpd.conf file.
Enable an optional stream wrapper to convert short tags to long tags on the fly:
This registers Zend_View_Stream as a stream wrapper for view scripts, and will ensure that your code continues to work as if short tags were enabled.
View Stream Wrapper Degrades Performance
Usage of the stream wrapper will degrade performance of your application, though actual benchmarks are unavailable to quantify the amount of degradation. We recommend that you either enable short tags, convert your scripts to use full tags, or have a good partial and/or full page content caching strategy in place.
Typically, you'll only ever need to call on assign(), render(), or one of the methods for setting/adding filter, helper, and script paths. However, if you wish to extend Zend_View yourself, or need access to some of its internals, a number of accessors exist:
getVars() will return all assigned variables.
clearVars() will clear all assigned variables; useful when you wish to re-use a view object, but want to control what variables are available.
getScriptPath($script) will retrieve the resolved path to a given view script.
getScriptPaths() will retrieve all registered script paths.
getHelperPath($helper) will retrieve the resolved path to the named helper class.
getHelperPaths() will retrieve all registered helper paths.
getFilterPath($filter) will retrieve the resolved path to the named filter class.
getFilterPaths() will retrieve all registered filter paths.