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Variable Modifiers

Variable modifiers give power to the template designer. Assume you pass a very long text to a variable but in the layout the designer only has space for a short teaser text. Using modifers, the designer may apply a Truncate modifier that shortens the text you pass in your PHP script. And this is only one application for variable modifiers.

Introduction

Applying modifers is really a piece of cake. All you have to do is to use the <patTemplate:var/> tag instead of only enclosing the variable in { and }. Then you may use the 'modifier' attribute to set the modifier.

<patTemplate:tmpl name="page">
<div>
    <patTemplate:var name="myVar" modifier="nl2br"/>
</div>
</patTemplate:tmpl>

Variable modifiers will be applied to the value of a variable when parsing the template. There two types of modfifiers:

• You may use any PHP function as a variable modifier. The modifier must accept only a string as a parameter and also return a string. Perfect examples for variable modifiers are nl2br() or htmlentities().
• You may create custom modifiers, which provide extended functionality and which may be influenced by the attributes of the var tag.

Custom Modifiers

Custom Modifiers are subclasses of patTemplate_Modifier and have to be placed inside patTemplate/Modifier. The filename has to match the last part of the classname. That means if you would like to create a filter that truncates sentences you will have to create a new class 'patTemplate_Modifier_Truncate' and place it into 'patTemplate/Modifier/Truncate.php'. The class has to implement one method modify( string value, array params ) that has to return the modified value. You may do whatever you like inside this method to modify the value. patTemplate will pass two parameters to your method:

• string $value, the value of the variable
• array $params, an associative array containing all attributes of the var tag except the ones, that are used internally (name, default, copyFrom, modifier)

The truncate modifier could look like this:

<?PHP
/**
 * patTemplate modfifier Truncate
 *
 * $Id: modifiers.xml 34 2004-05-11 19:46:09Z schst $
 *
 * @package        patTemplate
 * @subpackage     Modifiers
 * @author        Stephan Schmidt <schst@php.net>
 */
class patTemplate_Modifier_Truncate extends patTemplate_Modifier
{
   /**
    * truncate the string
    *
    * @access    public
    * @param    string        value
    * @return    string       modified value
    */
    function modify( $value, $params = array() )
    {
        /**
         * no length specified
         */
        if( !isset( $params['length'] ) )
			return $value;

        /**
         * is shorter than the length
         */
        if( $params['length'] > strlen( $value ) )
			return $value;

        return substr( $value, 0, $params['length'] ) . '...';
    }
}
?>

If you copy this file to the Modifier folder, you may instantly use it in your template files, by specifying it in the modifier attribute of any <patTemplate:var/> tag.

<patTemplate:tmpl name="page">
<div>
   <patTemplate:var name="myVar" modifier="Truncate" length="50"/>
</div>
</patTemplate:tmpl>

If you now pass a value that is longer than 50 chars, the modifier will automatically truncate it, before inserting it into the template.