Reference

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. You can do so by writing classes that implement Zend\Filter\FilterInterface, which defines a single method, filter().

Example

namespace Application\Filter;

use Zend\Filter\FilterInterface;

class MyFilter implements FilterInterface
{
    public function filter($value)
    {
        // perform some transformation upon $value to arrive on $valueFiltered

        return $valueFiltered;
    }
}

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

$filterChain = new Zend\Filter\FilterChain();
$filterChain->attach(new Application\Filter\MyFilter());

Alternately, add it to the FilterPluginManager:

$filterChain = new Zend\Filter\FilterChain();
$filterChain
    ->getPluginManager()
    ->setInvokableClass('myfilter', Application\Filter\MyFilter::class)
$filterChain->attachByName('myfilter');