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
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( array( 'author' => 'Hernando de Soto', 'title' => 'The Mystery of Capitalism' ), array( 'author' => 'Henry Hazlitt', 'title' => 'Economics in One Lesson' ), array( 'author' => 'Milton Friedman', 'title' => 'Free to Choose' ) ); // now assign the book data to a Zend_View instance Zend_Loader::loadClass('Zend_View'); $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 $this point to the
instance properties and methods. (Variables assigned to the
instance by the controller are public properties of the
Zend_View instance). Thus, a very basic view script could
look like this:
if ($this->books): ?> <!-- A table of some books. --> <table> <tr> <th>Author</th> <th>Title</th> </tr> <?php foreach ($this->books as $key => $val): ?> <tr> <td><?php echo $this->escape($val['author']) ?></td> <td><?php echo $this->escape($val['title']) ?></td> </tr> <?php endforeach; ?> </table> <?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:
base/path/ helpers/ filters/ scripts/
This may be set via
addBasePath(), or the
basePathoption to the constructor.
encoding: indicate the character encoding to use with
htmlspecialchars(), and other operations. Defaults to ISO-8859-1 (latin1). May be set via
encodingoption to the constructor.
escape: indicate a callback to be used by
escape(). May be set via
escapeoption to the constructor.
filter: indicate a filter to use after rendering a view script. May be set via
addFilter(), or the
filteroption to the constructor.
Zend_Viewto emit notices and warnings when uninitialized view variables are accessed. This may be set by calling
strictVars(true)or passing the
strictVarsoption to the constructor.
In our examples and documentation, we make use of PHP short tags:
<?=. In addition, we
typically use the alternate
syntax for control structures. These are convenient
shorthands to use when writing view scripts, as they make the
constructs more terse, and keep statements on single lines.
That said, many developers prefer to use full tags for purposes of
validation or portability. For instance,
short_open_tag is disabled in the php.ini.recommended
file, and if you template XML in view scripts, short open tags will
cause the templates to fail validation.
Additionally, if you use short tags when the setting is off, then the view scripts will either cause errors or simply echo code to the user.
For this latter case, where you wish to use short tags but they are disabled, you have two options:
Turn on short tags in your
php_value "short_open_tag" "on"
This will only be possible if you are allowed to create and utilize
.htaccessfiles. This directive can also be added to your
Enable an optional stream wrapper to convert short tags to long tags on the fly:
Zend_View_Streamas 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
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.