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?

Urinalysis

Twig is just a template engine. You know it right? – Mindymine

You can use "attribute" function: twig.sensiolabs.org/doc/functions/attribute.html {% if attribute(array, key) is defined %} // do something {% endif %} – Carrot

@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. – Oceanic

Answer 1

Twig example:

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

Sporulate

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! – Terrijo

{% 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 – Kindness

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. – Coseismal

Answer 2

You can use the keys twig function

{% if myVar in someOtherArray|keys %}

Unguarded

This did the job for me, ty ! – Sy

This is bad if used in a loop... There are much better answers, such using 'is defined'.. e.g. {% if someOtherArray[myVar] is defined %} – Longing

This works better in cases where the keys are not machine friendly. E.g. array['not-friendly'] – Bomar

If you are using dynamic key name, this answer is best. – Sharma

Answer 3

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__')
        -%}

See also

• SO: Similar question related to non-existent or null variables
• SO: General purpose use of default filter

Ribera

Answer 4

SYMFONY 6

solution is quite simple TWIG is looking for variable passed when $this->render is called in Controller.

1. create your pack data like

                $options = [
                    'companyLogo' => $company->getCompanyLogoLink(),
                    'companyName' => $company->getCompanyShortname(),
                    'menuItem'    => $companyMenuCategories,
   
            ];
   

2. pass it to TWIG

   return $this->render('folder/template.html.twig', [ 'o' => $options, ]);

3. in twig just look for 'passed' key ( o ) and array data with it

      {% if o.companyName is defined %}
        {{ o.companyName }}
      {% endif %}
   

Ought