submit function not call
I'd do something like this:

$items['share/%'] = array(
  'page callback' =&gt; 'ym_alter_sharing_content',
  'page arguments' =&gt; array(1),
  'access callback' =&gt; 'user_is_logged_in',
  'type' =&gt; MENU_CALLBACK,
);


function ym_alter_sharing_content($some_arg = NULL) {
  module_load_include('inc', 'node', 'node.pages');
  $form = node_add('share');
  array_unshift($form['actions']['submit']['#submit'], 'ym_alter_sharing_sub');
  return render($form);
}


function ym_alter_sharing_sub($form, &amp;$form_state){
  //dsm($form_state['values']);
  var_dump($form_state['values']);
  die("kill for debugging");
}


EDIT:
Another suggestion:

module_load_include('inc', 'node', 'node.pages'); 
$node_type = 'YOURNODETYPE';
$form_id = $node_type . '_node_form';

$node = new stdClass();
$node-&gt;type = $node_type;
node_object_prepare($node);

$form = drupal_get_form($form_id, $node);
array_unshift($form['actions']['submit']['#submit'], 'ym_alter_sharing_sub');
return render($form);