making value checkbox appear

I have a problem with my code. I use codeigniter. I made a checkbox form with a code like this :

foreach ($get_student->result_array() as $row){ $select_student[$row['student_number']] = $row['student_name']; echo form_checkbox($select_student,$student_number,FALSE); }

then the result just like this, only the checkbox appears, the student's name or student number does not appear: eror