Вам необходимо создать новый array
с помощью индекса object_id
.
Пример:
<?
$array = array(
array('rank'=>0,'id'=>6,'object_id'=>3,'account_id'=>13),
array('rank'=>1,'id'=>7,'object_id'=>3,'account_id'=>565),
array('rank'=>2,'id'=>1823,'object_id'=>825,'account_id'=>563),
array('rank'=>3,'id'=>1824,'object_id'=>825,'account_id'=>564),
array('rank'=>4,'id'=>1825,'object_id'=>825,'account_id'=>565),
array('rank'=>5,'id'=>7187,'object_id'=>3113,'account_id'=>564),
array('rank'=>6,'id'=>7188,'object_id'=>3113,'account_id'=>565),
);
$newArray = array(); // initiliaze array
foreach ($array as $key => $value) {
$newArray[$value['object_id']][] = $value['account_id']; // save it in group
}
echo "<pre>";
print_r($newArray); // result
?>
Пример выполнения