- array_reduce: documentation ( source)
- var_export: documentation ( source)
- array_replace: documentation ( source)
- array_keys: documentation ( source)
<?php
$array = [
["2" => 6, "5" => 1],
["2" => 1, "5" => 3],
];
var_export(
array_reduce(
$array,
fn($result, $row) => array_reduce(
array_keys($row),
fn($res, $k) => isset($res[$k]) && $res[$k] >= $row[$k]
? $res
: array_replace($res, [$k => $row[$k]]),
$result
),
[]
)
);