if

The if statement in Twig is comparable with the if statements of PHP.

In the simplest form you can use it to test if an expression evaluates to true:

{% if online == false %}
    <p>Our website is in maintenance mode. Please, come back later.</p>
{% endif %}

You can also test if an array is not empty:

{% if users %}
    <ul>
        {% for user in users %}
            <li>{{ user.username|e }}</li>
        {% endfor %}
    </ul>
{% endif %}

Note

If you want to test if the variable is defined, use if users is defined instead.

You can also use not to check for values that evaluate to false:

{% if not user.subscribed %}
    <p>You are not subscribed to our mailing list.</p>
{% endif %}

For multiple conditions, and and or can be used:

{% if temperature > 18 and temperature < 27 %}
    <p>It's a nice day for a walk in the park.</p>
{% endif %}

For multiple branches elseif and else can be used like in PHP. You can use more complex expressions there too:

{% if product.stock > 10 %}
   Available
{% elseif product.stock > 0 %}
   Only {{ product.stock }} left!
{% else %}
   Sold-out!
{% endif %}

Note

The rules to determine if an expression is true or false are the same as in PHP; here are the edge cases rules:

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https://twig.symfony.com/doc/2.x/tags/if.html