comment per page settings How can I change "Default comments per page" array to my own. What hook I need to use, if it needed?
hook_form_FORM_ID_alter(&amp;$form, &amp;$form_state)
with FORM_ID = node_type_form

$form doesn't contain this value
Drupal pulls the number of comments per page from variable_get('comment_default_per_page' . $node-&gt;type).   Its default is 50.  To change this go to content type X -> edit, then save.

To change the 50 to something else, you can create you own custom module and have this code

function example_form_alter(&amp;$form, &amp;$form_state, $form_id) {
    if ($form_id == 'node_type_form' &amp;&amp; isset($form['comment'])) {
        $form['comment']['comment_default_per_page']['#default_value'] = 70;
    }   
}




If you want to change it somewhere else,  then I recommend calling variable_set('comment_default_per_page' . $node-&gt;type,  'MYVALUE').  See below where it is hard-coded
inside comment.module &amp; comment_form:

$form['comment']['comment_default_per_page'] = array(
  '#type' =&gt; 'select',
  '#title' =&gt; t('Default comments per page'),
  '#default_value' =&gt; variable_get('comment_default_per_page_'. $form['#node_type']-&gt;type, 50),
  '#options' =&gt; _comment_per_page(),
  '#description' =&gt; t('Default number of comments for each page: more comments are distributed in several pages.'),
);


function _comment_get_display_setting($setting, $node) {
  global $user;

  if (isset($_GET[$setting])) {
    $value = $_GET[$setting];
  }
  else {
    // get the setting's site default
    switch ($setting) {
      case 'mode':
        $default = variable_get('comment_default_mode_'. $node-&gt;type, COMMENT_MODE_THREADED_EXPANDED);
        break;
      case 'sort':
        $default = variable_get('comment_default_order_'. $node-&gt;type, COMMENT_ORDER_NEWEST_FIRST);
        break;
      case 'comments_per_page':
        $default = variable_get('comment_default_per_page_'. $node-&gt;type, 50);
    }
...


and inside comment_render($node, $cid = 0) {

$comments_per_page = _comment_get_display_setting('comments_per_page', $node);