code: public static function unicode_to_utf16($str)
  	{
  		if (\extension_loaded('mbstring'))
  		{
  			return preg_replace_callback(
  				'/\\\\u([0-9a-fA-F]{4})/',
  				function ($match)
  				{
  					return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UTF-16BE');
  				},
  				$str
  			);
  		}
  
  		return $str;
  	}
docs: Converts Unicode sequences to UTF-16 string.
  
  @param   string  $str  Unicode string to convert
  
  @return  string  UTF-16 string
  
  @since   1.3.0