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 kenny.sick %}
Kenny is sick.
{% elseif kenny.dead %}
You killed Kenny! You bastard!!!
{% else %}
Kenny looks okay --- so far
{% 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:
Value | Boolean evaluation |
---|---|
empty string | false |
numeric zero | false |
whitespace-only string | true |
empty array | false |
null | false |
non-empty array | true |
object | true |