What are the differences between fetch and fetchAll methods in PDO when retrieving data from a database table?

The main difference between fetch and fetchAll methods in PDO when retrieving data from a database table is that fetch retrieves a single row from the result set, while fetchAll retrieves all rows from the result set. Fetch returns a single row as an associative array, while fetchAll returns an array containing all rows as associative arrays. To fetch a single row from a database table using fetch method: 

$stmt = $pdo->query("SELECT * FROM users");
$row = $stmt->fetch(PDO::FETCH_ASSOC);
print_r($row);
```

To fetch all rows from a database table using fetchAll method:

```php
$stmt = $pdo->query("SELECT * FROM users");
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($rows as $row) {
    print_r($row);
}

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