Replace Ci L

:::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 the "haystack" string with all occurrences of $needle replaced by $replacement (case-insensitive)

namespace HH\Lib\Str;

function replace_ci_l(
  \HH\Lib\Locale\Locale $locale,
  string $haystack,
  string $needle,
  string $replacement,
): string;

Locale-specific rules for case-insensitive comparisons will be used, and strings will be normalized before comparing if the locale specifies an encoding that supports multiple representations of the same characters, such as UTF-8.

• For a case-sensitive search/replace, see Str\replace_l().
• For multiple case-sensitive searches/replacements, see Str\replace_every_l().
• For multiple case-insensitive searches/replacements, see Str\replace_every_ci_l().

Guide

• String

Parameters

• \HH\Lib\Locale\Locale $locale
• string $haystack
• string $needle
• string $replacement

Returns

• string