vyber prvkov - POLIA

$query = "SELECT DISTINCT * FROM publication_bibtex ORDER BY p_bibtex_sk"; 
  $pole = array_query($query);
  $text .= "<select name='search_bibtex' size='3' multiple>\n";
    for($j=0; $j<count($pole); $j++)
      {
        $selected = ($pole[$j]['p_bibtex_id'] == intval($_POST['search_bibtex'])) ? " selected='selected'" : "";
        $text .= "\t<option value='".$pole[$j]['p_bibtex_id']."'".$selected.">".$pole[$j]['p_bibtex_sk']."</option>\n";
      }
  $text .= "</select>\n";

$selected = ($pole[$j]['p_bibtex_id'] == intval($_POST['search_bibtex'])) ? " selected='selected'" : "";

$selected = (in_array($pole[$j]['p_bibtex_id'], $_POST['search_bibtex'])) ? " selected='selected'" : "";

$selected = (in_array($pole[$j]['p_bibtex_id'], $_POST['search_bibtex'])) ? " selected='selected'" : "";

Warning: in_array() expects parameter 2 to be array, null given in C:\xampp\htdocs\kudao.php

if($_POST && is_array($_POST['search_bibtex'])) {
   ...
}