Why don't you just do something like this:
$query = 'SELECT * FROM your_table WHERE
your_key = 4
OR
your_key = 6
OR
your_key = 2
OR
your_key = 10';
$result = mysql_query($query) or die(mysql_error());
while ($row = mysql_fetch_assoc($result)) {
//do something
}
Or, if you don't know in advance which rows you will want (which would be weird), you can just increment the result set pointer manually using PHP's mysql_data_seek() function.