从多维数组生成<select>

I have a multidimensional array with this structure:

[
    {
        id: "2",
        optgroup: "Size Type A",
        valor: "40"
    },
    {
        id: "1",
        optgroup: "Size Type B",
        valor: "L"
    },
    {
        id: "3",
        optgroup: "Size Type B",
        valor: "XL"
    },
    {
        id: "4",
        optgroup: "Size Type A",
        valor: "41"
    }
]

My challenge is to create a select list with optgroup using "optgroud" key to arrange items in order.

Like this:

<select>
    <optgroup label="Size Type A">
        <option>40</option>
        <option>41</option>
    </optgroup>
    <optgroup label="Size Type B">
        <option>L</option>
        <option>XL</option>
    </optgroup>
</select>

But I can't find a way to do this. Any idea! Thanks a lot.

try this:

<?php

$array = [
    [
        "id" => 2,
        "optgroup"=> "Size Type A",
        "valor"=> 40
    ],
    [
        "id"=> 1,
        "optgroup"=> "Size Type B",
        "valor"=> "L"
    ],
    [
        "id"=> 3,
        "optgroup"=> "Size Type B",
        "valor"=> "XL"
    ],
    [
        "id"=> 4,
        "optgroup"=> "Size Type A",
        "valor"=> 41
    ]
];


$optgroups = [];
foreach ($array as $item){
    $optgroups[]=$item["optgroup"];
}
$optgroups = array_unique($optgroups);


?>
<select>
    <?php foreach ($optgroups as $optgroup){
        echo '<optgroup label="'.$optgroup.'">';
         foreach ($array as $item){
            if($item["optgroup"]==$optgroup){
                echo '<option>'.$item["valor"].'</option>';
            }
        }
        echo '</optgroup>';
    } ?>
</select>

<?php 

$items = [
    [
        'id'=> "2",
        'optgroup'=> "Size Type A",
        'valor'=> "40"
    ],
    [
        'id'=> "1",
        'optgroup'=> "Size Type B",
        'valor'=> "L"
    ],
    [
        'id' => "3",
        'optgroup' => "Size Type B",
        'valor'=> "XL"
    ],
    [
        'id' => "4",
        'optgroup' => "Size Type A",
        'valor' => "41"
    ]
];
$groups = [];
foreach($items as $i)
{
    $groups[$i['optgroup']]=[];
}

foreach($items as $i)
{
    array_push($groups[$i['optgroup']], $i);
}

echo '<select>';
foreach($groups as $key=>$g)
{
    echo '<optgroup label="'.$key.'">';
    foreach($g as $gg)
    {
        echo '<option>'.$gg['valor'].'</option>';
    }
    echo '</optgroup>';
}
echo '</select>';

This works for unlimited group names. First i split array to two parts by groups then i print it.