Writing Filters

Zend_Filter supplies a set of commonly needed filters, but developers will often need to write custom filters for their particular use cases. The task of writing a custom filter is facilitated by implementing Zend_Filter_Interface.

Zend_Filter_Interface defines a single method, filter(), that may be implemented by user classes. An object that implements this interface may be added to a filter chain with Zend_Filter::addFilter().

The following example demonstrates how to write a custom filter:

  1. class MyFilter implements Zend_Filter_Interface
  2. {
  3.     public function filter($value)
  4.     {
  5.         // perform some transformation upon $value to arrive on $valueFiltered
  7.         return $valueFiltered;
  8.     }
  9. }

To add an instance of the filter defined above to a filter chain:

  1. $filterChain = new Zend_Filter();
  2. $filterChain->addFilter(new MyFilter());
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