Twig Components / Methods / length

length is a Twig filter to return the number of items of a sequence or mapping, or the length of a string.

For objects that implement the Countable interface, length will use the return value of the count() method.

For objects that implement the __toString() magic method (and not Countable), it will return the length of the string provided by that method.

For objects that implement the Traversable interface, length will use the return value of the iterator_count() method.

{% if users|length > 10 %}
    ...
{% endif %}

Source: Twig