matkulSorting.php

<?php
    $array = array(
        array(
            'kode' => 'FIS15101',
            'nama' => 'Fisika Dasar',
            'sks' => '2',
            'nilai' => '4',
            'ak' => '8',
        ),
        array(
            'kode' => 'FIS15101L',
            'nama' => 'Praktikum Fisika Dasar',
            'sks' => '1',
            'nilai' => '3',
            'ak' => '3',
        ),
        array(
            'kode' => 'TW15101',
            'nama' => 'Praktek Tilawah',
            'sks' => '0',
            'nilai' => '',
            'ak' => '',
        ),
        array(
            'kode' => 'FIS15101L',
            'nama' => 'Praktikum Fisika Dasar',
            'sks' => '1',
            'nilai' => '4',
            'ak' => '4',
        ),
    );

    echo "<pre>";
    print_r($array);
    echo "<br>";
    print_r(unique($array));

    //based from https://stackoverflow.com/questions/55218253/find-duplicates-in-associative-array-php-compare-their-values

    function unique($matkulArray) {
        $keep = [];
        $tmp = array_column($matkulArray, 'kode');
        $dupes = array_diff(array_count_values($tmp), [1]);

        foreach($dupes as $key => $val){
            $res[$key] = max(array_intersect_key(array_column($matkulArray, 'nilai'), array_intersect($tmp, [$key])));

            $keep = array_filter(
                $matkulArray,
                function ($item) use ($res, $key) { 
                    return $item['kode'] == $key && $item['nilai'] == $res[$key];
                }
            );
        }

        foreach($matkulArray as $key => $val) {
            if(!array_key_exists($val['kode'], $res) || array_key_exists($key, $keep)) continue;
            unset($matkulArray[$key]);
        }

        return array_values($matkulArray);
    }

?>