php - Invalid argument supplied for checkbox -

my site showing warning:

invalid argument supplied foreach() in /admin/insert.php on line 37

i have used php code data insert in mysql database checkbox

how can solve it?

thanks

<table>     <tr>         <td bgcolor="#ffebc1">              <input type="checkbox" name="e1[]"value="1" >                 国語             <input type="checkbox" name="e1[]" value="2" >                 算数             <input type="checkbox" name="e1[]" value="3" >                 理科             <input type="checkbox" name="e1[]" value="4" >                 社会              <input type="checkbox" name="e1[]" value="5" >                 英語          </td>      </tr> </table> 

<?php  $ele_school = $_post['e1']; $selected_schoo2 = ""; foreach ($ele_school $ele_school2 ) {     $selected_schoo2 .= $ele_school2 . ", "; } $selected_schoo2 = substr($selected_schoo2, 0, -2); $query="insert  person(id,login_date,name,selected_schoo)      values('$_post[pid]',     '$_post[registration]',     '$_post[furigana2]',     '$selected_schoo2')";      mysql_query($query) or die("not insert".mysql_error()); ?> 

there might case data not coming $_post['e1'],

then in case executing foreach blank array, need is

if(isset($ele_school) && $ele_school != null){      foreach($ele_school $ele_school2){      // script      } }