<?php

$allCategories = [
  0 => ["id" => 1, "name" => "Elbise"],
  1 => ["id" => 2, "name" => "Şapka"],
  2 => ["id" => 3, "name" => "Podolski"],
];

$selectedCategories = [
  0 => 1,
  1 => 2
];

foreach ($allCategories as $category) {
  $selected = false;
  if (in_array($category["id"], $selectedCategories)) {
    $selected = true;
  }
}