Severity: Warning Message: sizeof(): Parameter must be an array or an object that implements Countable

Question

A PHP Error was encountered Severity: Warning
Message: sizeof(): Parameter must be an array or an object that implements Countable

Filename: administrator/nilai.php

Line Number: 139

for ($i=0; $i < sizeof($id_krs) ; $i++)
{
    $this->db->set('nilai', $nilai[$i])->where('id_krs',$id_krs[$i])->update('krs');
}

$data = array( 'id_krs' => $id_krs );