* @brief replaces a copy of string delimited by the start and (optionally) length parameters with the string given in replacement.
*
* @param string $input The input string. .Opposite to the PHP build-in function does not accept an array.
* @param $string
* @param string $replacement The replacement string.
* @param int $start If start is positive, the replacing will begin at the start'th offset into string. If start is negative, the replacing will begin at the start'th character from the end of string.
* @param int $length Length of the part to be replaced
* @param string $encoding The encoding parameter is the character encoding. Defaults to UTF-8
* @internal param string $input The input string. .Opposite to the PHP build-in function does not accept an array.