function microtime(bool $get_as_float = false*,*): string|float {}
function gettimeofday(bool $return_float = false*,*): array|float {}
function base64_decode(string $str, bool $strict = false*,*): string|false {}
function implode(string|array $glue, array $pieces*,*): string {}
function substr_replace(
string|array $str,
string|array $replace,
$start,
$length*,*
) : string|array|false {}