Overriding fetch() for PDO when fetching using foreach

3
votes

I have extended PDOStatement and modified the fetch() method to typecast values of the types timestamp and arrays, in PostgreSQL, to DateTime and native array. This works as intended but I can't override the behaviour when using the statement in a foreach.

I have solved this by returning rows into an object implementing ArrayAccess, IteratorAggregate and Countable. However I'm not satisfied with that solution and just want a pure array back.

Example:

class ExtendedStatement extends PDOStatement {
    protected function __construct() {
        $this->setFetchMode(PDO::FETCH_ASSOC);
    }
    public function fetch(
        $fetch_style = PDO::FETCH_ASSOC,
        $cursor_orientation = PDO::FETCH_ORI_NEXT,
        $cursor_offset = 0)
    {
        $r = parent::fetch($fetch_style, $cursor_orientation, $cursor_offset);
        if (is_array($r)) {
            $r["extradata"] = TRUE;
        }
        return $r;
    }
}
$db = new PDO("sqlite::memory:");
$db->setAttribute(
    PDO::ATTR_STATEMENT_CLASS, array("ExtendedStatement", array($db)));
$db->exec("CREATE TABLE example(id INTEGER PRIMARY KEY, name VARCHAR)");
$db->exec("INSERT INTO example(name) VALUES('test')");

// This is what is does
$s = $db->prepare("SELECT * FROM example");
$s->execute();
foreach ($s as $r) {
    var_dump($r);
}
$s->closeCursor();

// This is how I want it to be
$s = $db->prepare("SELECT * FROM example");
$s->execute();
while ($r = $s->fetch()) {
    var_dump($r);
}
$s->closeCursor();

// This is how I want it to be
$s = $db->prepare("SELECT * FROM example");
$s->execute();
var_dump($s->fetch());
$s->closeCursor();

Output:

array(2) {
  ["id"]=>
  string(1) "1"
  ["name"]=>
  string(4) "test"
}
array(3) {
  ["id"]=>
  string(1) "1"
  ["name"]=>
  string(4) "test"
  ["extradata"]=>
  bool(true)
}
array(3) {
  ["id"]=>
  string(1) "1"
  ["name"]=>
  string(4) "test"
  ["extradata"]=>
  bool(true)
}
2
phpooppdophp-5.3
Can you show some code that does work as expected, and does not work as expected? If you've overridden fetch, it should always work "correctly." - Charles
Updated with an example. - runfalk
Does it work normally when you replace the foreach with while($r = $s->fetch()) {? Also, keep in mind that the result returned by the parent::fetch call may well not be an array, it could be null. You should probably add an is_array check or something similar. - Charles
Yes it works as expected. My normal code works, but this starts looping to infinity. This code is just an example to demonstrate the bevaviour. This is not the real code. - runfalk

2 Answers

3
votes

The PDOStatement class implements the built-in internals-only Traversable interface. The iterator that it implements bypasses the public PDOStatement::fetch() method.

0
votes

I use something like this:

$db->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);
$sql = 'select * from table';
$stmt = $db->prepare($sql);
$stmt->execute();

while($row = $stmt->fetch(PDO::FETCH_ASSOC, PDO::FETCH_ORI_NEXT))
{
    // do stuff
}

So the only thing you have to do is set some options :)