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Input Filters
Input Filters are similar to Output Filters but are used in a totally different context. The let you filter the templates after they are read from the filesystem, database or any other location, but before the template is being parsed and analyzed.
Why input filters?
You may use input filters for various tasks. You could strip all whitespace from you templates to speed up the parsing process, remove unneeded comments or unpack templates if they are stored in zipped format. You may also use it in some special cases, where you need to modify the templates but are not able to modify them in their original storage location.
Implementing an Input Filter
Implementing an Input Filter is exactly the same as creating a new Output Filter. You have to extend a new class from patTemplate_InputFilter and place it in a file in the patTemplate/InputFilter directory. The last part of the class name has to be identical to the name of the file. In this class, you simply have to implement one method:
- string patTemplate_OutputFilter::apply( string templateCode )
patTemplate_Reader will pass the template code to this method before it is analyzed by the lexer and you may modify it according to your needs.
A simple example
The following example strips HTML comments from the templates before they are analyzed. This allows you to place them between the <patTemplate:tmpl> and <patTemplate:sub> tags, although it is not allowed to place data there.
<?PHP
/**
* patTemplate StripComments input filter
*
* Will remove all HTML comments.
*
* @package patTemplate
* @subpackage Filters
* @author Stephan Schmidt <schst@php.net>
*/
class patTemplate_InputFilter_StripComments extends patTemplate_InputFilter
{
/**
* filter name
*
* @access private
* @var string
*/
var $_name = 'StripComments';
/**
* compress the data
*
* @access public
* @param string data
* @return string data without whitespace
*/
function apply($data) {
$data = preg_replace('°<!--.*-->°msU', '', $data);
return $data;
}
}
?>
Applying input filters
Applying an input filter is an easy task. You just have to call one method on your patTemplate object and pass the desired output filter. You may create a filter chain by applying as many input filters as you like. If you applied more than one filter, the will be called in the same order as you applied them.
<?PHP
require_once 'pat/patErrorManager.php';
require_once 'pat/patTemplate.php';
$tmpl = &new patTemplate();
$tmpl->setRoot('templates');
$tmpl->applyInputFilter('StripComments');
$tmpl->readTemplatesFromInput('page.tmpl', 'File');
/**
* output filter will be applied here
*/
$tmpl->displayParsedTemplate();
?>
Passing parameters to the filter
You may also create an input filter that can be parameterised by the script that applies the filter. If the filter class needs to access the parameters set by the script, you may use the method patTemplate_InputFilter::getParam(). When applying a filter, all parameters have to be passed as an array in the second parameter of patTemplate::applyInputFilter().
