Get Taxonomy Term ID by Node in Drupal 8 - drupal-8

Question

I'm trying to get Taxonomy data by particular node.
How can I get Taxonomy Term Id by using Node object ?
Drupal ver. 8.3.6

Answer 1

You could do something like that:
$termId = $node->get('field_yourfield')->target_id;
Then you can load the term with
Term::load($termId);
Hope this helps.

Answer 2

If you want to get Taxonomy Term data you can use this code:
$node->get('field_yourfield')->referencedEntities();
Hope it will be useful for you.
PS: If you need just Term's id you can use this:
$node->get('field_yourfield')->getValue();
You will get something like this:
[0 => ['target_id' => 23], 1 => ['target_id'] => 25]
In example my field has 2 referenced taxonomy terms.
Thanks!

Answer 3

#Kevin Wenger's comment helped me. I'm totally basing this answer on his comment.
In your code, when you have access to a fully loaded \Drupal\node\Entity\Node you can access all the (deeply) nested properties.
In this example, I've got a node which has a taxonomy term field "field_site". The "field_site" term itself has a plain text field "field_site_url_base". In order to get the value of the "field_site_url_base", I can use the following:
$site_base_url = $node->get('field_site')->entity->field_site_url_base->value;

Answer 4

How to extract multiple term IDs easily if you know a little Laravel (specifically Collections):
Setup: composer require tightenco/collect to make Collections available in Drupal.
// see #Wau's answer for this first bit...
// remember: if you want the whole Term object, use ->referencedEntities()
$field_value = $node->get('field_yourfield')->getValue();
// then use collections to avoid loops etc.
$targets = collect($field_value)->pluck('target_id')->toArray();
// $targets = [1,2,3...]
or maybe you'd like the term IDs comma-separated? (I used this for programmatically passing contextual filter arguments to a view, which requires , (OR) or + (AND) to specify multiple values.)
$targets = collect($field_value)->implode('target_id', ',');
// $targets = "1,2,3"