PHP-Foreach变量仅在读取时有效

Question

I am trying to read posts under each category as shown below. There are multiple categories with id "4", "3", "2", "1". Only for category "1" there is a post available.

foreach ($wp_categories as $wp_category) {

  $id = $wp_category->term_taxonomy_id;
  //if($id == "1") {
   $posts = $json_api->introspector->get_posts(array(
                  'cat' => $id
                  ));
  //}
  $result[] = $posts;         
}

return $result;

In the above code if I just uncomment the if condition, I am getting the posts in the result array. But if this is commented I am not getting the posts in result.

I am new to PHP and above condition is not making any sense. It would be of great help if someone could explain why having the if condition is making the post available in the result.

dumping $wp_categories below

{
  "status": "ok",
  "0": {
    "term_id": "5",
    "name": "Category 5",
    "slug": "category5",
    "term_group": "0",
    "term_order": "1",
    "term_taxonomy_id": "5",
    "taxonomy": "category",
    "description": "",
    "parent": "0",
    "count": "0"
  },
  "1": {
    "term_id": "2",
    "name": "Category 4",
    "slug": "category4",
    "term_group": "0",
    "term_order": "2",
    "term_taxonomy_id": "2",
    "taxonomy": "category",
    "description": "",
    "parent": "0",
    "count": "0"
  },
  "2": {
    "term_id": "3",
    "name": "Category 3",
    "slug": "category3",
    "term_group": "0",
    "term_order": "3",
    "term_taxonomy_id": "3",
    "taxonomy": "category",
    "description": "",
    "parent": "0",
    "count": "0"
  },
  "3": {
    "term_id": "4",
    "name": "abc",
    "slug": "abc",
    "term_group": "0",
    "term_order": "4",
    "term_taxonomy_id": "4",
    "taxonomy": "category",
    "description": "",
    "parent": "0",
    "count": "0"
  },
  "4": {
    "term_id": "1",
    "name": "Others",
    "slug": "others",
    "term_group": "0",
    "term_order": "5",
    "term_taxonomy_id": "1",
    "taxonomy": "category",
    "description": "",
    "parent": "0",
    "count": "1"
  }
}

Answer 1

This is simply shows that it will be true only in case of id 1:

if($id == "1") {

I think this should be:

if(isset($id) && $id != '') {

to get the all the post.