drupal напрямую не поддерживает элемент
http://api.drupal.org/api/drupal/includes--form.inc/function/theme_button/6
<?php
function phptemplate_button($element) {
// Make sure not to overwrite classes.
if (isset($element['#attributes']['class'])) {
$element['#attributes']['class'] = 'form-' . $element['#button_type'] . ' ' . $element['#attributes']['class'];
}
else {
$element['#attributes']['class'] = 'form-' . $element['#button_type'];
}
if ($element['#button_type'] == 'button') {
// return a fancy html button.
return '<button ' . (empty($element['#name']) ? '' : 'name="' . $element['#name'] . '" ') . 'id="' . $element['#id'] . '" ' . drupal_attributes($element['#attributes']) . ">" . check_plain($element['#value']) . "</button>\n";
} else {
// retain the normal functionality for anything else
return '<input type="submit" ' . (empty($element['#name']) ? '' : 'name="' . $element['#name'] . '" ') . 'id="' . $element['#id'] . '" value="' . check_plain($element['#value']) . '" ' . drupal_attributes($element['#attributes']) . " />\n";
}
}
?>
тогда ваш код для вызова этого будет:
$form['content']['search'] = array(
'#type' => 'submit',
'#button_type' => 'button',
'#name' => 'search',
'#value' => t('Search'),
'#attributes' => array('class' => 'btn', 'title'=>'Submit Search')
);
, который должен выдавать:
<button id="edit-search" class="form-button btn" title="Submit Search" name="search" >Search</button>
протестировано в Drupal 6.