In Twig, check if a specific key of an array exists

Question

In PHP we can check if a key exists in an array by using the function array_key_exists().

In the Twig templating language we can check if an variable or an object's property exists simply by using an if statement, like this:

{% if app.user %}
do something here
{% else %}
do something else
{% endif %}

But how do we check if a key of an array exists using Twig? I tried {% if array.key %}, but it gives me an error:

Key "key" for array with keys "0, 1, 2, 3...648" does not exist

As one of the primary ways of passing data into a template is using arrays, it seems like there should be some way of doing this. Any thoughts?

You can use "attribute" function: http://twig.sensiolabs.org/doc/functions/attribute.html {% if attribute(array, key) is defined %} // do something {% endif %} — Dennais, Mar 13 '15 at 14:47
@Vega You should add that as an answer, as it seems to be the only way to check for a key that isn't a single word, like `data-value`. — insertusernamehere, Oct 26 '15 at 10:09

score 236 · Accepted Answer · answered Nov 28 '12 at 14:29

236

Twig example:

{% if array.key is defined %}
  // do something
{% else %}
  // do something else
{% endif %}

answered Nov 28 '12 at 14:29

phpisuber01

7,585
3
22
26

2

Why can't we just use `{% if array.key %}`? What's wrong with it? In JS it's perfectly valid statement but not in Twig! – Dmitry Feb 11 '16 at 18:49
3

`{% if array.key %}` is valid, but it's the syntax to check if the array key is empty. [twig.sensiolabs.org/doc/tags/if.html#if](http://twig.sensiolabs.org/doc/tags/if.html#if) – bats-everywhere Aug 28 '16 at 05:02
30

If key is a variable, you need to use `{% if array[ key ] %}` or `{% if array[ key ] is defined %}`. `array.key` tries to access index 'key' in the array. – MarthyM Dec 01 '16 at 08:36

score 38 · Answer 2 · answered Jan 23 '17 at 21:23

38

You can use the keys twig function

{% if myVar in someOtherArray|keys %}

answered Jan 23 '17 at 21:23

Samir Patel

805
7
9

1

This did the job for me, ty ! – Marcky May 18 '17 at 16:00
5

This is bad if used in a loop... There are much better answers, such using 'is defined'.. e.g. {% if someOtherArray[myVar] is defined %} – Steve Childs Mar 08 '18 at 11:16
2

This works better in cases where the keys are not machine friendly. E.g. array['not-friendly'] – burntblark Oct 29 '19 at 12:07
1

If you are using dynamic key name, this answer is best. – maverabil Jul 19 '21 at 13:12

score 4 · Answer 3 · edited May 23 '17 at 12:10

Quick Answer (TL;DR)

DeveloperTLindel wants to test for existence of array key in Twig.
DeveloperTLindel wants to trap any errors associated with undefined key.
This can be handled using the default filter.

Detailed Answer

Context

Twig 2.x (latest version as of Wed 2017-03-08)
General-purpose use of the default filter.

Problem

Scenario:
DeveloperTLindel wants to test for existence of array key in Twig.
DeveloperTLindel wants to avoid any errors or exceptions caused by potentially undefined key.

Solution

DeveloperTLindel can use the default filter.
The default filter catches any exceptions owing to undefined variable, and allows short-circuit substition of an alternate value.
The default filter is chainable.

Example01


{#- ****************************************
  testing for a single key in associative array
  -#} 
  {%- set mystring = myarray['key-no-existo'] |default('__BLANK__')  -%}

{#- ****************************************
  testing for a multiple keys in associative array
  -#} 
  {%- set mystring = myarray['alpha']
        |default(myarray['bravo'])
        |default(myarray['charlie'])
        |default('__BLANK__')
        -%}