How to Dynamically Access Twig Variable Names?

Dynamically Accessing Twig Variable Names

Accessing variables with dynamic names in Twig can be a challenge. Consider the following scenario:

<p>placeholder1
placeholder2
placeholderx
</p>

<pre class="brush:php;toolbar:false">{% for invoices as invoice %}
    need to display here the placeholder followed by the invoice id number
    {{ placeholedr1 }}

Accessing Variables with Context Array

Instead of using the attribute function, you can access variable values in the _context array using bracket notation:

{{ _context['placeholder' ~ id] }}

This option is more concise and arguably clearer.

Strict Variable Checks

When strict_variables is set to true in the environment options, you may encounter errors for non-existent variables. To handle this, use the default filter:

{{ _context['placeholder' ~ id]|default }}

{{ attribute(_context, 'placeholder' ~ id)|default }}

Checking Variable Existence

To check if a variable exists before accessing it, use the defined test:

{% if _context['placeholder' ~ id] is defined %} ... {% endif %}

Default Values with the default Filter

Provide a default value in case the variable doesn't exist using |default:

{{ _context['placeholder' ~ id]|default(null) }}

{{ attribute(_context, 'placeholder' ~ id)|default('Default value') }}

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