json decode call photo telegram api - php

Question

i want get photo file id.
file_get_contents('php://input'):
{
"update_id": 399206890,
"message": {
"message_id": 149,
"from": {
"id": 81777999,
"is_bot": false,
"first_name": "#goldenguardbot",
"last_name": "✅",
"username": "amirntm",
"language_code": "en-US"
},
"chat": {
"id": 81777999,
"first_name": "#goldenguardbot",
"last_name": "✅",
"username": "amirntm",
"type": "private"
},
"date": 1507643430,
"photo": [
{
"file_id": "AgADBAADpaoxG6lZ6VIeePTlKxaJsl3X-RkABPbjyThHJgF7FLwBAAEC",
"file_size": 1639,
"file_path": "photos/file_4.jpg",
"width": 90,
"height": 72
},
{
"file_id": "AgADBAADpaoxG6lZ6VIeePTlKxaJsl3X-RkABIrarvPZGVNGFrwBAAEC",
"file_size": 22230,
"width": 320,
"height": 256
},
{
"file_id": "AgADBAADpaoxG6lZ6VIeePTlKxaJsl3X-RkABKFhu79tL5EBF7wBAAEC",
"file_size": 95422,
"width": 800,
"height": 640
},
{
"file_id": "AgADBAADpaoxG6lZ6VIeePTlKxaJsl3X-RkABGzlLqe_Yv0PFbwBAAEC",
"file_size": 172689,
"width": 1160,
"height": 928
}
]
}
}
i want file id how get it?
for example:
$update->message->photo->file_id;

Answer 1

The "photo" section is an array. Square brackets in JSON ([]) indicate an indexed array. Curly braces ({}) indicate an object or associative array, depending on how you choose to parse it in PHP.
You don't mention which "file_id" you want, but assuming you want the first:
$update = json_decode(file_get_contents('php://input'));
echo $update->message->photo[0]->file_id;

Answer 2

You need to decode it to PHP object/array, and get photos in $update->message->photo, that will be array of one photo in different resolution, the latest one always be largest, so you can use end($photos) to get it, and file_id is corresponding file identity.
Code example:
$json = file_get_contents('php://input'):
$update = json_decode($json);
$photos = $update->message->photo;
$photo = end($photo);
$file_id = $photo['file_id'];