Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Shared/StringHelper.php
public static function convertEncoding($value, $to, $from)
    {
        if (self::getIsIconvEnabled()) {
            $result = iconv($from, $to . '//IGNORE//TRANSLIT', $value);
            if (false !== $result) {
                return $result;
            }
        }

        return mb_convert_encoding($value, $to, $from);
    }
public static function convertEncoding($value, $to, $from)
    {
        if (self::getIsIconvEnabled()) {
            $result = iconv($from, $to . '//IGNORE//TRANSLIT', $value);
            if (false !== $result) {
                return $result;
            }
        }

        return mb_convert_encoding($value, $to, $from);
    }
Convert string from one encoding to another.

@param string $value
@param string $to Encoding to convert to, e.g. 'UTF-8'
@param string $from Encoding to convert from, e.g. 'UTF-16LE'

@return string