code: public function getKey($input)
      {
          // try matching the key with plain text
          foreach ($this->text as $key => $code) {
              if ($code === $input) {
                  return $key;
              }
          }
  
          // try matching the key with ascii
          foreach ($this->ascii as $key => $code) {
              if (chr($code) === $input) {
                  return $key;
              }
          }
  
          // try matching the key with unicode
          foreach ($this->unicode as $key => $code) {
              if (unicode_to_string($code) === $input) {
                  return $key;
              }
          }
  
          return false;
      }
docs: Fetches a human readable key representation
  based on a unicode/ascii/plain text charset
  
  @param string $input unicode string
  
  @return bool|int|string