在PDO中缺少mysql_ *的一些有用功能

Question

I'd like to have a MySQL query or table object, say one that takes PDO object as input and doing all the necessary stuff with the table.

I was thinking that this object could implement some array interfaces, like Countable , ArrayAccess , Iterator so I could easily foreach the rows like it was a regular array.

In deprecated mysql_* functions there was (still is, yet) very useful function mysql_data_seek() , which helped to move row-by-row, so I could implement all Iterator methods. I could run one query at the beginning and keep the rows in some resource private field and serve if I needed to.

The other functions (mostly informational, like mysql_list_tables() and similar) I can cover by sending proper query to the db and fetch the result, but how could I move to specific row?

I thought that the last parameter of the fetch() method is the cursor position, but when I call

$p = $database->query('SELECT * FROM tobjects');
$row = $p->fetch(PDO::FETCH_ASSOC, PDO::ATTR_CURSOR,$i);

it's always resulting the same row for any value of $i .

EDIT

Actually, it's not the same row, but the first row at the first call to fetch() , second row for second etc., like there was no cursor information. As suggested in answers I did this

$p = $database->prepare('SELECT * FROM tobjects',
                    array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$p->execute();
$row = $p->fetch(PDO::FETCH_ASSOC, PDO::FETCH_ORI_ABS, $i);

but this works the same.

Answer 1

You are using PDO::ATTR_CURSOR wrong. What you need to do is request a scrollable cursor first by using PDO::prepare , and then you can move to any record you want in the result set:

$s = $database->prepare('SELECT * FROM tobjects',
                        [PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL]);
$s->execute();
$row = $s->fetch(PDO::FETCH_ASSOC, PDO::FETCH_ORI_ABS, $i);

Answer 2

I don't find any of these functions useful for whatever real life scenario.

mysql_list_tables() indeed can be substituted with WAY more informative and flexible query to INFORMATION SCHEMA

Why bother with implementing ArrayAccess if you can have a regular array already? There are only 2 scenarios:

• either you need relatively small amount of data, fits for the web page. Just select it all at once.

   $data = $stmt->fetchAll(); 

  And you can traverse the resulting array whatever way you like.

• or you need to traverse long table in some sort of console service script. You don't need traverse it back and forth then. Just select and loop over.