select 2 multiple

<?php

$dbsetup = [
  'host' => 'localhost',
  'user' => 'gunawan',
  'pass' => 'ya4i8ib2',
  'name' => 'gun_learning'
];

$conn =new PDO("mysql:host=" . $dbsetup['host'] . ";dbname=" . $dbsetup['name'] . "", $dbsetup['user'], $dbsetup['pass']);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
//--------------------
if($act=='data')
{
    $result=[];
    // $result[]=[
        // 'id'=>-1,
        // 'text'=>'Silahkan memilih dari pilihan dibawah'
    // ];
    $type = $_GET['type']??'none';
    $search = $_GET['search']??NULL;
    if($type=='prod')
    {

        $cat = $_GET['category']??NULL;
        if($cat==NULL || (int)$cat == 0)
        {
            $result=[];
            $result[]=[
                'id'=>-1,
                'text'=>'Silahkan memilih Category'
            ];

        }
        else
        {
            if(!is_array($cat))
            {
                $sql="select nama from tb_category where id=?";
                $que = $conn->prepare($sql);
                $que->bindValue(1, $cat);
                $que->execute();
                $cat_name = $que->fetchColumn();
                $raw[ ]=$sql;

                if(strlen($search)<3)
                {
                    $sql="select id, nama from tb_prod where cat_id=? limit 5";
                    $que = $conn->prepare($sql);
                    $que->bindValue(1, $cat);
                }
                else
                {
                    $sql="select id, nama from tb_prod where  cat_id=? and nama like ? limit 5";
                    $que = $conn->prepare($sql);
                    $que->bindValue(1, $cat);
                    $que->bindValue(2, "%$search%");
                }
                $raw[ ]=$sql;
                $que->execute();
                $data=[];$children=[];
                while($row = $que->fetch())
                {
                    $result0[]=[
                        'id'=>$row['id'],
                        'text'=>$row['nama']
                    ];
                    $children[]=[
                        'id'=>$row['id'],
                        'text'=>$row['nama']
                    ];
                    $data[]=$row;
                }
                $result[]=[
                    'text'=>$cat_name,
                    'children'=>$children
                ];
                $raw[]='single cat';
            }
            else
            {
                foreach($cat as $id_cat)
                {
                    $sql="select nama from tb_category where id=?";
                    $que = $conn->prepare($sql);
                    $que->bindValue(1, $id_cat);
                    $que->execute();
                    $cat_name = $que->fetchColumn();
                    $raw[ ]=$sql;

                    if(strlen($search)<3)
                    {
                        $sql="select id, nama from tb_prod where cat_id=? limit 5";
                        $que = $conn->prepare($sql);
                        $que->bindValue(1, $id_cat);
                    }
                    else
                    {
                        $sql="select id, nama from tb_prod where  cat_id=? and nama like ? limit 5";
                        $que = $conn->prepare($sql);
                        $que->bindValue(1, $id_cat);
                        $que->bindValue(2, "%$search%");
                    }
                    $raw[ ]=$sql;
                    $que->execute();
                    $data=[];$children=[];
                    while($row = $que->fetch())
                    {
                        $result0[]=[
                            'id'=>$row['id'],
                            'text'=>$row['nama']
                        ];
                        $children[]=[
                            'id'=>$row['id'],
                            'text'=>$row['nama']
                        ];
                        $data[]=$row;
                    }
                    $result[]=[
                        'text'=>$cat_name,
                        'children'=>$children
                    ];
                }

                $raw[]='arr cat';
            }

            $raw['data']=$data;
        }

    }

    if($type=='category')
    {
        if(strlen($search)<3)
        {
            $sql="select id, nama from tb_category";
            $que = $conn->prepare($sql);
        }
        else
        {
            $sql="select id, nama from tb_category where nama like ?";
            $que = $conn->prepare($sql);
            $que->bindValue(1, "%$search%");
        }

        $que->execute();
        $data=[];
        while($row = $que->fetch())
        {
            $result[]=[
                'id'=>$row['id'],
                'text'=>$row['nama']
            ];
            $data[]=$row;
        }
        $raw['data']=$data;
    }

    $return=[
        'results'=>$result,
        'params'=>$_GET,
        'raws'=>@$raw
    ];

    echo json_encode($return);
    die;

}
?>
<html lang="en">
<head>
    <title>jquery select2 ajax php example</title>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.min.css" integrity="sha256-aAr2Zpq8MZ+YA/D6JtRD3xtrwpEz2IqOS+pWD/7XKIw=" crossorigin="anonymous" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.5.0/js/bootstrap.min.js" integrity="sha256-OFRAJNoaD8L3Br5lglV7VyLRf0itmoBzWUoM+Sji4/8=" crossorigin="anonymous"></script>
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.js"></script>

<link href="https://cdn.jsdelivr.net/npm/select2@4.1.0-rc.0/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdn.jsdelivr.net/npm/select2@4.1.0-rc.0/dist/js/select2.min.js"></script>
<style>
    .select-js{
        width:200px;
    }
    body{
        padding:10px 20px;
    }
</style>
</head>
<body>
<form>
<!--br/>Test  <select class='select-js js-data-example-ajax'><option>Pilih Repo</option></select-->
<br/>Kategori
<select class='select-js select-cat' multiple="multiple"><option>Pilih kategori tersedia</option></select>
<br/>Barang  <select class='select-js select-prod'><option>Pilih kategori terlebih dahulu</option></select>
</form>

<script>
$(document).ready(function() {
    $('.js-data-example-ajax, .select-cat').select2({
      ajax: {
        url: 'index.php?act=data',
        dataType: 'json',
        // Additional AJAX parameters go here; see the end of this chapter for the full code of this example
        data: function(params)
        {
            var query={
                search:params.term,
                type:'category'
            };
            return query;
        },
        processResults: function (data) {
            return {
              results: data.results
            };
        },
      }
    });
    $('.select-cat').on("select2:select", function(e) {
        $(".select-prod").empty();
        //console.log('see');// what you would like to happen
    });

    $('.select-prod').select2({
      ajax: {
        url: 'index.php?act=data',
        dataType: 'json',
        // Additional AJAX parameters go here; see the end of this chapter for the full code of this example
        data: function(params)
        {
            var query={
                search:params.term,
                type:'prod',
                category:$(".select-cat").val()
            };
            return query;
        },
        processResults: function (data) {
            return {
              results: data.results
            };
        },
      }
    });

});

</script>

</body>
</html>