It's often useful and/or necessary to perform some normalization on
input prior to validation. For example, you may want to strip out
all HTML, but run your validations on what remains to ensure the
submission is valid. Or you may want to trim empty space surrounding input so that a
StringLength validator will use the correct length of the input without counting leading
or trailing whitespace characters. These operations may be performed using
Zend_Filter. Zend_Form_Element has support
for filter chains, allowing you to specify multiple, sequential filters. Filtering
happens both during validation and when you retrieve the element value via
getValue():
<?php
$filtered = $element->getValue();
Filters may be added to the chain in two ways:
passing in a concrete filter instance
providing a short filter name
Let's see some examples:
<?php
// Concrete filter instance:
$element->addFilter(new Zend_Filter_Alnum());
// Short filter name:
$element->addFilter('Alnum');
$element->addFilter('alnum');
Short names are typically the filter name minus the prefix. In the default case, this will mean minus the 'Zend_Filter_' prefix. The first letter can be upper-cased or lower-cased.
Using Custom Filter Classes
If you have your own set of filter classes, you can tell
Zend_Form_Element about these using
addPrefixPath(). For instance, if you have
filters under the 'My_Filter' prefix, you can tell
Zend_Form_Element about this as follows:
<?php
$element->addPrefixPath('My_Filter', 'My/Filter/', 'filter');
(Recall that the third argument indicates which plugin loader on which to perform the action.)
If at any time you need the unfiltered value, use the
getUnfilteredValue() method:
<?php
$unfiltered = $element->getUnfilteredValue();
For more information on filters, see the Zend_Filter documentation.
Methods associated with filters include:
addFilter($nameOfFilter, array $options = null)addFilters(array $filters)setFilters(array $filters)(overwrites all filters)getFilter($name)(retrieve a filter object by name)getFilters()(retrieve all filters)removeFilter($name)(remove filter by name)clearFilters()(remove all filters)