Requires the Hack Standard Library to be installed.

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<T as HH\Lib\Regex\Match>(
  string $haystack,
    Pattern<T> $pattern,
  int $offset = 0,
): bool;

Throws Invariant[Violation]Exception if $offset is not within plus/minus the length of $haystack.


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