Basic Syntax

Expression Lab uses the Symfony Expression Language component as the foundational engine for evaluating expressions. It provides a declarative Domain-Specific Language designed for querying, transforming data, and interacting with WordPress services without writing raw PHP scripts.

Want to learn more?

See the Symfony's The Expression Syntax official documentation for further reference.

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Language Engine Overview

The Symfony Expression Language component compiles expressions into Abstract Syntax Tree (AST) structures. While expression-oriented (evaluating to a single result without imperative loops like while or for), Expression Lab extends the base language with a declarative functional scripting layer (prog[...], set[...], fn[...], map[...]).

This enables multi-step execution pipelines, expression state management, and lambda transformations while restricting execution to registered operators and functions.

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Literals & Primitive Types

Expression Lab supports standard data primitives:

Type	Syntax Examples	Description
Numbers	42, 3.14, -10, 1e3	Integers and floating-point values.
Strings	'hello', "WordPress", "Value with \"quotes\""	Single or double-quoted strings.
Booleans	true, false	Case-insensitive boolean literals.
Null	null	Represents an empty or null value.

String Escaping

Strings can be enclosed in single quotes ('...') or double quotes ("..."). When you need to include quote marks or backslashes within a string, follow standard escape rules:

• Single quotes ('...'): Escape internal single quotes with a backslash (\'), e.g., 'It\'s a test'.
• Double quotes ("..."): Escape internal double quotes with a backslash (\"), e.g., "He said \"Hello\"".
• Literal backslashes: Escape backslashes with a double backslash (\\), e.g., 'C:\\Windows' or "path\\to\\file".
• Pro Tip: You can alternate quote delimiters to avoid escaping entirely:
  • Use double quotes to enclose single quotes: "It's a test"
  • Use single quotes to enclose double quotes: 'He said "Hello"'

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Collections & Data Structures

Arrays (Lists)

Arrays are comma-separated values enclosed in square brackets [...]:

[1, 2, 3, "four", true]

Elements are accessed via zero-based numeric indexing:

users[0]

Maps (Key-Value Objects)

Key-value maps are enclosed in curly braces {...}:

{ id: 1, title: 'Sample Post', published: true }

Property access can be performed using either dot notation or bracket notation:

post.title
post['title']

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Operators

Expression Lab provides a comprehensive set of operators for arithmetic, comparison, logical evaluation, and string manipulation.

Arithmetic Operators

Operator	Syntax	Description
+	10 + 5	Addition (returns 15)
-	10 - 5	Subtraction (returns 5)
*	10 * 5	Multiplication (returns 50)
/	10 / 5	Division (returns 2)
%	10 % 3	Modulo (returns 1)
**	2 ** 3	Exponentiation (returns 8)

String Concatenation

Use the ~ (tilde) operator to concatenate strings:

'Hello, ' ~ Users.current.data.display_name ~ '!'

Comparison Operators

Operator	Syntax	Description
==	status == 'publish'	Loose equality
===	user_id === 1	Strict equality
!=	post_type != 'revision'	Loose inequality
!==	role !== 'subscriber'	Strict inequality
<, >	count > 10	Less than, greater than
<=, >=	memory <= 50	Less than or equal, greater than or equal

Logical Operators

Operator	Syntax	Description
and / &&	is_admin and has_access	Logical AND
or / ||	is_editor or is_admin	Logical OR
not / !	not is_draft	Logical NOT

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Advanced Operators

Ternary Operator (condition ? true_val : false_val)

user.is_admin ? 'Administrator' : 'Standard User'

Null Coalescing Operator (??)

Returns the first operand if it exists and is not null, otherwise returns the second:

post.meta['subtitle'] ?? 'No subtitle available'

Membership Operators (in, not in)

Check whether an element is present in an array or string:

'administrator' in Users.current.roles

'draft' not in ['publish', 'future', 'private']

Regular Expression Matching (matches)

Test strings against regular expressions:

Users.current.data.user_email matches '/^[a-zA-Z0-9._%+-]+@example\\.com$/'

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Method Calls & Object Access

You can invoke methods on any exposed service or model object:

Options.get('active_plugins')

Methods can be chained fluidly:

Posts.where('post_status','publish').get()

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Next Steps

• Learn multi-step execution, expression variables, closures, and stream transformations in Scripting Syntax.
• Explore runtime helpers and constants in Functions and Constants.
• Learn how to query and mirror data in Database.
• Configure environment safety brakes and keys in Configuration.