t.php

<?php

$data = array(
	'Collections' => array(
		'id' => 1,
		'name' => 'Countries',
	),
	// sorted by group,name from the SQL
	'CollectionItems' => array(
		array( 'id' => 1, 'collection_id' => 1, 'name' => 'CountryName', 'value' => 'Cyprus', 'group' => 1,),
		array( 'id' => 2, 'collection_id' => 1, 'name' => 'CountryCode', 'value' => 'CY', 'group' => 1,),
		array( 'id' => 3, 'collection_id' => 1, 'name' => 'PhoneCode', 'value' => '357', 'group' => 1,),
		array( 'id' => 10, 'collection_id' => 1, 'name' => 'Home', 'value' => true, 'group' => 1,),
		
		array( 'id' => 4, 'collection_id' => 1, 'name' => 'CountryName', 'value' => 'Russia', 'group' => 4,),
		array( 'id' => 5, 'collection_id' => 1, 'name' => 'CountryCode', 'value' => 'RU', 'group' => 4,),
		array( 'id' => 6, 'collection_id' => 1, 'name' => 'PhoneCode', 'value' => '7', 'group' => 4,),
	),
);


$wanted = array(
	array('id' => 1, 'CountryName' => 'Cyprus', 'CountryCode' => 'CY', 'PhoneCode' => '357'),	
	array('id' => 4, 'CountryName' => 'Russia', 'CountryCode' => 'RU', 'PhoneCode' => '7'),	
);

$actual = array();
$last_group = null;
$current_item = array();
foreach ($data['CollectionItems'] as $item) {
	if (!is_null($last_group) && ($last_group <> $item['group'])) {
		$actual[] = $current_item;
		$current_item = array();
	}
	$current_item[ $item['name'] ] = $item['value'];
	$last_group = $item['group'];
}
$actual[] = $current_item;


print_r($actual);
?>