_{Official ZPE/YASS documentation}Querying data with ZEQL

Overview

ZEQL (ZPE Expression Query Language, pronounced zequel) provides a concise way to filter and transform an iterable value. A query uses the familiar from, in, where and select keywords.

ZEQL queries are lazy. The source is enumerated when the result is consumed, not when the query is declared. A query variable exists only inside its query.

A first query

$numbers = [1, 2, 3, 4, 5]

$doubled = from $number in $numbers
  select $number * 2

print($doubled.to_list())
  

The expression following select is evaluated for every item. It can return the original value, a calculated value, or a value taken from an object or map.

Filtering with where

$numbers = [1, 2, 3, 4, 5, 6]

$even_squares = from $number in $numbers
  where $number % 2 == 0
  select $number * $number

print($even_squares.to_list()) //[4, 16, 36]
  

The optional where expression must produce a boolean. Values for which it returns false are skipped before the projection is evaluated.

Using query results

A ZEQL expression returns a ZPEExpressionQuery. It supports these operations:

to_list() ⇒ list

Enumerates the complete query and returns an ordinary list.

length() ⇒ number

Counts the values produced by the query.

first() ⇒ mixed

Returns the first matching value, or undefined when no value matches.

Because a query is lazy, enumerate it only when the result is needed. Use first() when only one match is required instead of converting the entire result to a list.

Related collection methods

Lists and maps also provide where, select and order_by methods for fluent collection pipelines:

$names = ["Jimmy", "James", "Jack", "John"]
$result = $names
  .where($name => string_contains($name, "a"))
  .select($name => $name)
  .order_by($name => $name)
  

ZEQL was made available in ZPE 1.14.9 (Spurriergate, September 2026).