Matches

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Returns whether a match exists in $haystack given the regex pattern $pattern and an optional offset at which to start the search

namespace HH\Lib\Regex;

function matches(
  string $haystack,
  Pattern<Match> $pattern,
  int $offset = 0,
): bool;

The regex pattern follows the PCRE library: https://www.pcre.org/original/doc/html/pcresyntax.html.

Throws InvariantException if $offset is not within plus/minus the length of $haystack.

Guide

• String

Parameters

• string $haystack
• Pattern<Match> $pattern
• int $offset = 0

Returns

• bool