1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
``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``:
.. code-block:: html+twig
{% 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:
.. code-block:: html+twig
{% 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``:
.. code-block:: html+twig
{% if not user.subscribed %}
<p>You are not subscribed to our mailing list.</p>
{% endif %}
For multiple conditions, ``and`` and ``or`` can be used:
.. code-block:: html+twig
{% 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:
.. code-block:: twig
{% 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
====================== ====================
|
