Converting Zend Db ResultSet to PHP Arrays with toArray()

When to use Zend\Db\ResultSet\ResultSet::toArray()

Call toArray() on a valid Zend\Db\ResultSet\ResultSet to obtain a plain PHP array where each element represents a row. The method uses the ResultSet’s hydrator; if no hydrator is set, each row becomes a stdClass object with column names as properties.

Worked example

use Zend\Db\Adapter\Adapter;
use Zend\Db\Sql\Sql;
use Zend\Db\ResultSet\ResultSet;

// Assume $adapter is a configured Zend\Db\Adapter\Adapter instance
$sql   = new Sql($adapter);
$select = $sql->select()->from('users')->where->equalTo('status', 'active');
$statement = $sql->prepareStatementForSqlObject($select);
$result    = $statement->execute();

// $result is a ResultSet object
$resultSet = new ResultSet();
// Optionally set a hydrator, e.g., ArrayHydrator for plain arrays
// $resultSet->setHydrator(new Zend\Stdlib\Hydrator\ArrayHydrator());

$rows = $resultSet->initialize($result)->toArray();

// $rows is now an array of stdClass objects (or hydrated arrays)
foreach ($rows as $row) {
    echo $row->username . PHP_EOL;
}

How the mechanism works

• The ResultSet holds a reference to the executed statement.
• When toArray() is invoked, it iterates over the statement, fetches each row, and passes the row data through the configured hydrator.
• If the hydrator is null, the default behavior creates a stdClass instance and assigns column values as properties.
• The method returns a new PHP array containing all hydrated rows.

Limits and common mistakes

1. Memory consumption – toArray() materializes every row in memory. For large result sets consider pagination (LIMIT/OFFSET) or iterating with current()/next() on the ResultSet instead.
2. Closed or invalid ResultSet – Calling toArray() after the statement has been closed or after a previous fetch that exhausted the cursor throws a BadMethodCallException. Always ensure the ResultSet is initialized ($resultSet->initialize($result)) and not reused.
3. Hydrator mismatch – If you set a hydrator that expects specific object types (e.g., an ObjectPropertyHydrator for a User entity) but the ResultSet contains columns that do not map, you may get incomplete objects or exceptions. Verify the hydrator with $resultSet->getHydrator() before conversion.
4. Unexpected data types – The hydrator does not perform type conversion; database values remain as strings unless the hydrator or your application casts them.

Performance considerations

Because toArray() builds the entire result set in memory, its time complexity is O(n) with a significant constant factor due to object hydration. For result sets under a few thousand rows the overhead is usually acceptable. Beyond that, consider using $resultSet->toArray() on a limited slice (LIMIT) or iterating with while ($row = $resultSet->current()) { … $resultSet->next(); } to keep memory usage flat.

Practical verification

After calling toArray(), you can check the result:

• Use var_dump($rows); to inspect structure and data types.
• Confirm row count with count($rows); matches the expected number of rows from the query.
• If a hydrator was set, verify that the first element is an instance of the expected class: if ($rows[0] instanceof MyEntity) { … }.