php mysql query iterator

queryiterator.php

<?php

class QueryIterator implements Iterator 
{
    private $position = 0;
    private $rows=array();
    private $result = NULL;
    
    public function __construct($sql) 
    {
        $this->sql = $sql;
        $this->result = mysql_query($this->sql);
    }
    
    function rewind() 
    {
        $this->position = 0;
    }

    function current() 
    {
        return $this->rows[$this->position];
    }

    function key() 
    {
        return $this->position;
    }

    function next() 
    {
        $this->position++;
    }

    function valid() 
    {
        if ($this->result && FALSE !== ($row = mysql_fetch_assoc($this->result))) 
        {
            $this->rows[]=$row;
        }
        return isset($this->rows[$this->position]);
    }
    
}

//usage
$rows = new QueryIterator("SELECT * FROM users");
foreach($rows as $row)
  print_r($row);