1``if``
2======
3
4The ``if`` statement in Twig is comparable with the if statements of PHP.
5
6In the simplest form you can use it to test if an expression evaluates to
7``true``:
8
9.. code-block:: html+twig
10
11    {% if online == false %}
12        <p>Our website is in maintenance mode. Please, come back later.</p>
13    {% endif %}
14
15You can also test if an array is not empty:
16
17.. code-block:: html+twig
18
19    {% if users %}
20        <ul>
21            {% for user in users %}
22                <li>{{ user.username|e }}</li>
23            {% endfor %}
24        </ul>
25    {% endif %}
26
27.. note::
28
29    If you want to test if the variable is defined, use ``if users is
30    defined`` instead.
31
32You can also use ``not`` to check for values that evaluate to ``false``:
33
34.. code-block:: html+twig
35
36    {% if not user.subscribed %}
37        <p>You are not subscribed to our mailing list.</p>
38    {% endif %}
39
40For multiple conditions, ``and`` and ``or`` can be used:
41
42.. code-block:: html+twig
43
44    {% if temperature > 18 and temperature < 27 %}
45        <p>It's a nice day for a walk in the park.</p>
46    {% endif %}
47
48For multiple branches ``elseif`` and ``else`` can be used like in PHP. You can
49use more complex ``expressions`` there too:
50
51.. code-block:: twig
52
53    {% if product.stock > 10 %}
54       Available
55    {% elseif product.stock > 0 %}
56       Only {{ product.stock }} left!
57    {% else %}
58       Sold-out!
59    {% endif %}
60
61.. note::
62
63    The rules to determine if an expression is ``true`` or ``false`` are the
64    same as in PHP; here are the edge cases rules:
65
66    ====================== ====================
67    Value                  Boolean evaluation
68    ====================== ====================
69    empty string           false
70    numeric zero           false
71    NAN (Not A Number)     true
72    INF (Infinity)         true
73    whitespace-only string true
74    string "0" or '0'      false
75    empty array            false
76    null                   false
77    non-empty array        true
78    object                 true
79    ====================== ====================
80