API@RTK0.NET

1. drupal
   1. 4.7 filter_example.module
   2. 5 filter_example.module
   3. 6

Implementation of hook_filter().

The bulk of filtering work is done here. This hook is quite complicated, so we'll discuss each operation it defines.

Related topics

Example: Filter

Defining a filter in a module. (drupal 6)

Code

examples/filter_example/filter_example.module, line 63

<?php
function filter_example_filter($op, $delta = 0, $format = -1, $text = '') {
  // The "list" operation provides the module an opportunity to declare both how
  // many filters it defines and a human-readable name for each filter. Note that
  // the returned name should be passed through t() for translation.
  if ($op == 'list') {
    return array(
      0 => t('Substitute "foo"'), 
      1 => t('Current time'),
    );
  }

  // All operations besides "list" provide a $delta argument so we know which
  // filter they refer to. We'll switch on that argument now so that we can
  // discuss each filter in turn.
  switch ($delta) {

    // First we define the simple string substitution filter.
    case 0:

      switch ($op) {
        // This description is shown in the administrative interface, unlike the
        // filter tips which are shown in the content editing interface.
        case 'description':
          return t('Substitutes a custom string for the string "foo" in the text.');

          // We don't need the "prepare" operation for this filter, but it's required
          // to at least return the input text as-is.
        case 'prepare':
          return $text;

          // The actual filtering is performed here. The supplied text should be
          // returned, once any necessary substitutions have taken place.
        case 'process':
          return str_replace('foo', variable_get("filter_example_foo_$format", 'bar'), $text);

          // Since we allow the administrator to define the string that gets
          // substituted when "foo" is encountered, we need to provide an
          // interface for this customization. Note that the value of $format
          // needs to be provided as part of the form name, so that different
          // customization can be done for this filter in each of the different
          // input formats that may use it.
        case 'settings':
          $form['filter_example'] = array(
            '#type' => 'fieldset', 
            '#title' => t('Foo filter'), 
            '#collapsible' => TRUE, 
            '#collapsed' => TRUE,
          );
          $form['filter_example']["filter_example_foo_$format"] = array(
            '#type' => 'textfield', 
            '#title' => t('Substitution string'), 
            '#default_value' => variable_get("filter_example_foo_$format", 'bar'), 
            '#description' => t('The string to substitute for "foo" everywhere in the text.'),
          );
          return $form;
      }
      break;

      // Next is our "time tag" filter.
    case 1:

      switch ($op) {
        // This description is shown in the administrative interface, unlike the
        // filter tips which are shown in the content editing interface.
        case 'description':
          return t('Inserts the current time in the place of a &lt;time /&gt; tags.');

          // Since this filter will return a different result on each page load, we
          // need to return TRUE for "no cache" to ensure that the filter is run
          // every time the text is requested. Setting this to TRUE will force
          // every filter in associated input formats to be run on every access,
          // so only disable caching if absolutely required.
        case 'no cache':
          return TRUE;

          // This filter is a little trickier to implement than the previous one.
          // Since the input involves special HTML characters (< and >) we have to
          // run the filter before HTML is escaped/stripped by other filters. But
          // we want to use HTML in our result as well, and so if we run this filter
          // first our replacement string could be escaped or stripped. The solution
          // is to use the "prepare" operation to escape the special characters, and
          // to later replace our escaped version in the "process" step.
          //
          // We'll use [filter-example-time] as a replacement for the time tag.
          // Note that in a more complicated filter a closing tag may also be
          // required. For more information, see "Temporary placeholders and
          // delimiters" at http://drupal.org/node/209715.
        case 'prepare':
          return preg_replace('!<time ?/>!', '[filter-example-time]', $text);

          // Now, in the "process" step, we'll search for our escaped time tags and
          // to the real filtering.
        case 'process':
          return str_replace('[filter-example-time]', '<em>' . format_date(time()) . '</em>', $text);
      }
      break;
  }
}
?>