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:
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{% if online == false %}
<p>Our website is in maintenance mode. Please, come back later.</p>
{% endif %}You can also test if a sequence or a mapping is not empty:
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{% 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:
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{% if not user.subscribed %}
<p>You are not subscribed to our mailing list.</p>
{% endif %}For multiple conditions, and and or can be used:
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{% 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:
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{% 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:
| Value | Boolean evaluation |
|---|---|
| empty string | false |
| numeric zero | false |
| NAN (Not A Number) | true |
| INF (Infinity) | true |
| whitespace-only string | true |
| string "0" or '0' | false |
| empty sequence | false |
| empty mapping | false |
| null | false |
| non-empty sequence | true |
| non-empty mapping | true |
| object | true |