Hook dans module

function filter_exemple_preprocess_node($vars)
{
       print_r($vars);
}

function filter_exemple_filter($op, $delta = 0, $format = -1, $text = '') {
 

  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;
return "prepare";

        // The actual filtering is performed here. The supplied text should be
        // returned, once any necessary substitutions have taken place.
        case 'process':
          return str_replace('a', 'e', $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 <time /> 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);
return "prepare";