Formulário php marcado quando o valor da caixa de seleção na consulta mysql da matriz?

<label>Select State</label><br>
<?php 
$allgroup = mysql_query("SELECT * FROM  state");
$flag=false;
while($state_list = mysql_fetch_array($allgroup))
{
   $parr=explode(',',$er['state_id']);
   $size = sizeof($parr);
   for($i=0;$i<$size;$i++) { 
     if($parr[$i]==$state_list['id']) {                              
        $flag=true;
     } 
   }    

  if($flag==true) {
    ?>
    <input  type='checkbox' name='state[]' style="margin-left:5px;" value="<?php echo $state_list['id']; ?>" checked  > <?php echo $state_list['name']; ?> <br>
    <?php
    $flag=false;
  } else { 
    ?>
    <input  type='checkbox' name='state[]' style="margin-left:5px;" value="<?php echo $state_list['id']; ?>"     > <?php echo $state_list['name']; ?> <br>
    <?php
    }
}
?>

<?php
$states="";
$i=0;
foreach( $_POST['state'] as $selected) {
   echo sizeof($_POST['state']);
   if($i==sizeof($_POST['state'])-1) {
       $states = $states.$selected;
   } else {
     $states = $states.$selected.",";
   }
   $i++;
}
?>