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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?

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  • Twig is just a template engine. You know it right? Commented Nov 28, 2012 at 14:28
  • 4
    You can use "attribute" function: twig.sensiolabs.org/doc/functions/attribute.html {% if attribute(array, key) is defined %} // do something {% endif %} Commented Mar 13, 2015 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. Commented Oct 26, 2015 at 10:09

4 Answers 4

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Twig example:

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

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!
{% 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
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.
47

You can use the keys twig function

{% if myVar in someOtherArray|keys %}

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This did the job for me, ty !
This is bad if used in a loop... There are much better answers, such using 'is defined'.. e.g. {% if someOtherArray[myVar] is defined %}
This works better in cases where the keys are not machine friendly. E.g. array['not-friendly']
If you are using dynamic key name, this answer is best.
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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

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2

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 %}
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