php - IN() with string as parameter not working with PDO -

I am trying to change a mysql_query statement that has the following in PDF:

 < Code> $ string = '2, 3, 4, 5, 7, 8';   
 
  mysql_query ("... IN ($ string) ...");   
 It works properly  mysql_query  statement, but it will not work with the PDO preparation and execution (no results have been returned).  
 What am I missing here?  
 
 
 
 If the query works well with SQL  mysql_query  Will work fine with.  
 Will not work if you tie the whole string with just one placeholder. You need to bind each value for the  IN  section.  
   Example:    
  $ string = '2, 3, 4, 5, 7, 8'; $ Params = Explosion (',', $ string); $ Sth = $ pdo- & gt; Ready (include '... IN ('. ',' Array_fill (0, count ($ params), '?')). '' ... ...); $ Ret = $ sth- & gt; Execute ($ params);