mb_substr
Introduction
Human Language and Character Encoding Support
PHP Manual

# GNU Recode

- Introduction
- Installing/Configuring
  - Installation
  - Runtime Configuration
  - Resource Types
- Predefined Constants
- Recode Functions
  - recode_file — Recode from file to file according to recode request
  - recode_string — Recode a string according to a recode request
  - recode — Alias of recode_string

mb_substr
Introduction
Human Language and Character Encoding Support
PHP Manual