Expressions & Syntax

Full reference for Unblock's expression syntax.

Unblock uses Twig expression syntax — widely used and well-documented.

Accessing Data

Use dot notation to access properties:

{{ post.title }}
{{ post.author.name }}
{{ site.name }}

Bracket notation for array elements or dynamic properties:

{{ array[0] }}
{{ array['key'] }}

Optional chaining for properties that might be null:

{{ post.author?.name }}
{{ post.thumbnail?.src }}

Method calls with arguments:

{{ post.date('F j, Y') }}
{{ user.avatar(96) }}
{{ post.meta('field_name') }}

Conditional Logic

Ternary Operator

{{ condition ? 'yes' : 'no' }}
{{ post.thumbnail ? 'Has image' : 'No image' }}
{{ user.id ? user.name : 'Guest' }}
{{ user.id ? 'Welcome!' }}                    <!-- Empty if guest -->

Fallback Operators

Operator	Name	Returns fallback when
??	Null coalescing	Value is null
?:	Elvis	Value is falsy (null, false, 0, '', [])
|default	Default filter	Value is empty (like ?: but preserves 0)

{{ post.subtitle ?? 'No subtitle' }}
{{ post.image ?? post.thumbnail ?? '/default.jpg' }}
{{ post.views ?: 0 }}
{{ post.subtitle|default('No subtitle') }}

Comparison:

Value	??	?:	|default
'text'	'text'	'text'	'text'
null	fallback	fallback	fallback
false	false	fallback	fallback
0	0	fallback	0
''	''	fallback	fallback
[]	[]	fallback	fallback

Operators

Arithmetic

Operator	Description	Example
+	Addition / Concatenation	{{ 5 + 3 }} → 8
-	Subtraction	{{ 10 - 3 }} → 7
*	Multiplication	{{ 4 * 5 }} → 20
/	Division	{{ 20 / 4 }} → 5
%	Modulo	{{ 17 % 5 }} → 2
//	Floor division	{{ 17 // 5 }} → 3
**	Power	{{ 2 ** 3 }} → 8
..	Range	{{ 1..5 }} → [1, 2, 3, 4, 5]

Comparison

Operator	Description	Example
==	Equal	{{ a == b }}
!=	Not equal	{{ a != b }}
===	Identical	{{ a === b }}
!==	Not identical	{{ a !== b }}
<	Less than	{{ a < b }}
>	Greater than	{{ a > b }}
<=	Less or equal	{{ a <= b }}
>=	Greater or equal	{{ a >= b }}
<=>	Spaceship	{{ a <=> b }}

Logical

Operator	Description	Example
and	Logical AND	{{ a and b }}
or	Logical OR	{{ a or b }}
not	Logical NOT	{{ not a }}

String & Containment

Operator	Description	Example
~	Concatenation (cast to string)	{{ 'Hello ' ~ name }}
+	Concatenation (auto-detect)	{{ post.title + ' - ' + site.name }}
starts with	Starts with test	{{ post.title starts with 'Hello' }}
ends with	Ends with test	{{ post.slug ends with '-draft' }}
in	Contains	{{ 'a' in ['a', 'b'] }}
not in	Not contains	{{ 'c' not in ['a', 'b'] }}

+ concatenates when either side is a string, otherwise adds numbers. ~ always concatenates.

Operator Precedence

From lowest to highest priority:

1. ? — Ternary
2. or — Logical OR
3. ??, ?: — Fallback
4. and — Logical AND
5. ==, !=, <, >, <=, >=, <=>, in, not in, starts with, ends with — Comparison
6. .. — Range
7. +, -, ~ — Addition / Concatenation
8. *, /, %, // — Multiplication / Division
9. ** — Power (right-associative)
10. not — Logical NOT
11. | — Filter

{{ (a + b) * c }}
{{ (value ?? 'default')|upper }}
{{ (post.views ?: 0) + 1 }}
{{ post.title|upper == 'HELLO' }}             <!-- Filter binds before comparison -->

Literals

{{ 'single quotes' }}          {{ "double quotes" }}
{{ 42 }}                       {{ 3.14 }}                {{ -10 }}
{{ true }}                     {{ false }}               {{ null }}
{{ [1, 2, 3] }}                {{ ['a', 'b', 'c'] }}
{{ {key: 'value'} }}           {{ {name: 'John', age: 30} }}

Arrow Functions

Used with higher-order filters like map, filter, sort, reduce, and find:

{{ items|map(p => p.name) }}
{{ items|filter(p => p.active) }}
{{ items|find(p => p.id == 5) }}
{{ items|sort((a, b) => a.date <=> b.date) }}
{{ items|reduce((carry, item) => carry + item.price, 0) }}
{{ posts|filter(p => p.status == 'publish' and p.author.id == user.id) }}

Escaping & Output

All output is automatically escaped — you never need to think about it. UnBlock combines two layers of protection:

• Field-aware: each field knows its type. Text fields use esc_html, URL fields like post.link use esc_url, and HTML fields like post.content are already processed by WordPress.
• Context-aware: expressions in HTML attributes are escaped with esc_attr (or esc_url for URL attributes like href and src), regardless of the field used.

{{ post.title }}                <!-- esc_html in text, esc_attr in attributes -->
{{ post.link }}                 <!-- esc_url everywhere -->
{{ post.content }}              <!-- Pre-processed HTML, safe to output -->

Comments are not rendered in the output:

{# This is a comment #}

Error Handling

Missing properties return an empty string — no errors. Properties are safely navigated even through null:

{{ post.nonexistent }}         <!-- Returns '' -->
{{ post.author.name }}         <!-- Safe even if author is null -->

Common mistake

Watch operator precedence when combining filters with fallback operators. {{ value ?? 'default'|upper }} applies upper to 'default' only — not to the whole result. Use parentheses: {{ (value ?? 'default')|upper }}.

Reserved Keywords

Cannot be used as variable names: true, false, null, none, and, or, not, in, if.

Next steps

• Your First Expression — learn the basics step by step
• Providers — all available data fields
• Filters — transform and format data
• Functions — built-in utility and WordPress functions
• Common Patterns — ready-to-use template examples