defined is a Twig test to check 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 %}Source: Twig