How to make if _from is Alone to _to --- to Select _Alone with the higher ID
Drop else from array
array (
0 =>
array (
'id' => '8',
'_from' => '2',
'_to' => '1',
'date' => '2018-10-15 15:51:07',
'message' => 'ccccccxxxxx',
'read' => '0',
'feedback' => '0',
'cnt' => '3',
),
1 =>
array (
'id' => '6',
'_from' => '1',
'_to' => '2',
'date' => '2018-10-15 15:47:01',
'message' => 'zzzzzzz1',
'read' => '1',
'feedback' => '0',
'cnt' => '1',
),
If you have small arrays, It is not a problem to run the algorithm with complexity O(n2). But for me better is less clear, but faster algorithm with complexity equals to O(2n)
$array = array(
array(
'id' => 12,
'_from' => 1,
'_to' => 2
),
array(
'id' => 13,
'_from' => 4,
'_to' => 2
),
array(
'id' => 14,
'_from' => 2,
'_to' => 1
),
);
$newArray = [];
foreach ($array as $item) {
$uniqueRecordKey = $item['_from'].'-'.$item['_to'];
$oppositeRecordKey = $item['_to'].'-'.$item['_from'];
//If exists record from the opposite and new ID is greater than previous put
if (isset($newArray[$oppositeRecordKey])) {
$newArray[$oppositeRecordKey] = $item;
continue; //Do not append to the end
}
$newArray[$uniqueRecordKey] = $item;
}
var_dump($newArray);