Please check below code, I hope this is help full for you.
$resultArray = uniqueAssocArray($actualArray, 'RecipientID');
function uniqueAssocArray($array, $uniqueKey) {
if (!is_array($array)) {
return array();
}
$uniqueKeys = array();
foreach ($array as $key => $item) {
$groupBy=$item[$uniqueKey];
if (isset( $uniqueKeys[$groupBy]))
{
//compare $item with $uniqueKeys[$groupBy] and decide if you
//want to use the new item
$replace= false;
}
else
{
$replace=true;
}
if ($replace) $uniqueKeys[$groupBy] = $item;
}
return $uniqueKeys;
}