This method converts a PDOStatement object into an Iterator object, making it convenient for iterating over the result set of the PDOStatement. The returned Iterator represents each row of the result set.

Return Value:
Returns an Iterator representing the PDOStatement object.

<?php
// Establish a database connection
$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');

// Prepare and execute an SQL query
$stmt = $pdo->query('SELECT * FROM mytable');

// Convert PDOStatement to an Iterator
$iterator = $stmt->getIterator();

// Process the result set using a loop
foreach ($iterator as $row) {
    // $row represents a row of the result set
    print_r($row);
}

// Close the PDOStatement and the connection
$stmt = null;
$pdo = null;
?>

One detail to add to what berxudar said.
Because this statement comes from the IteratorAggregate interface, it is recognized by foreach() directly, meaning there's no need to collect the iterator just to make a foreach().

Editing the code according to this :

<?php
// Establish a database connection
$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');

// Prepare and execute an SQL query
$stmt = $pdo->query('SELECT * FROM mytable');

// Process the result set using a loop
foreach ($stmt as $row) {
    // $row represents a row of the result set
    print_r($row);
}

// Close the PDOStatement and the connection
$stmt = null;
$pdo = null;
?>
Note we gave $stmt to foreach() directly. Foreach() will see that $stmt is a PDOStatement object and as such is an object of IteratorAggregate, and will call on its own this method to get an iterator to work with.