php - Switch placement of values in comma delimited string -

i have comma delimited string held within database field contain number of values:

23,45,21,40,67,22 

i need able somehow switch 2 values, example know need move 45 1 position down string, end with:

23,21,45,40,67,22 

the reason numbers correspond ids held in database table, , position in sting determine order items printed on screen. before ask database design - i've inherited , cannot changed without significant work entire application.

so i've thought exploding string, identifying position of target number , swapping 1 next-door, i'm unsure of how can achieved when total number of values not known.

any things? suspect solution cumbersome, needs must!!

assuming need move desired value down 1 position in array:

$values = explode(',', $data_string);  $value_to_move = 45;  $value_count = count($values); for($i=0;$i<$value_count;$i++) {     if($values[$i] == $value_to_move)     {         if($i < ($value_count-1))         {   // if value move not @ end of list             $values[$i] = $values[$i+1];             $values[$i+1] = $value_to_move;             $i++;         }     } } $new_data_string = implode(',', $values);