Built-in Twig tests

constant

constant checks if a variable has the exact same value as a constant. You can use either global constants or class constants:

{% if post.status is constant('Post::PUBLISHED') %}
    the status attribute is exactly the same as Post::PUBLISHED
{% endif %}

You can test constants from object instances as well:

{% if post.status is constant('PUBLISHED', post) %}
    the status attribute is exactly the same as Post::PUBLISHED
{% endif %}

defined

defined checks if a variable is defined in the current context. This is very useful if you use the strict_variables option:

{# defined works with variable names #}
{% if foo is defined %}
...
{% endif %}

{# and attributes on variables names #}
{% if foo.bar is defined %}
...
{% endif %}

{% if foo['bar'] is defined %}
...
{% endif %}

When using the defined test on an expression that uses variables in some method calls, be sure that they are all defined first:

{% if var is defined and foo.method(var) is defined %}
...
{% endif %}

divisible by

divisible by checks if a variable is divisible by a number:

{% if loop.index is divisible by(3) %}
...
{% endif %}

empty

empty checks if a variable is an empty string, an empty array, an empty hash, exactly false, or exactly null.

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

For objects that implement the __toString() magic method (and not Countable), it will check if an empty string is returned.

{% if foo is empty %}
...
{% endif %}

even

even returns true if the given number is even:

{{ var is even }}

iterable

iterable checks if a variable is an array or a traversable object:

{# evaluates to true if the foo variable is iterable #}
{% if users is iterable %}
    {% for user in users %}
        Hello {{ user }}!
    {% endfor %}
{% else %}
    {# users is probably a string #}
    Hello {{ users }}!
{% endif %}

null

null returns true if the variable is null:

{{ var is null }}

Note

none is an alias for null.

odd

odd returns true if the given number is odd:

{{ var is odd }}

same as

same as checks if a variable is the same as another variable. This is equivalent to === in PHP:

{% if foo.attribute is same as(false) %}
    the foo attribute really is the 'false' PHP value
{% endif %}