On Mon, Oct 21, 2019 at 5:03 PM Colin O'Dell <colinodell@gmail.com> wrote:
> Hello Internals,
>
> Is there any particular reason why the substr() function doesn't accept a
> null $length like mb_substr() does? It seems the behavior to read through
> the end of the string can only be controlled by the presence or absence of
> the $length parameter: https://3v4l.org/YpuO1
>
> I discovered this discrepancy between the two methods while attempting to
> create a specialized string wrapper class with a method like this:
>
> public function getSubstring(int $start, ?int $length = null): string
> {
> if ($this->isMultibyte) {
> return mb_substr($this->line, $start, $length,
> $this->encoding);
> } else {
> return substr($this->line, $start, $length);
> }
> }
>
> This method would not work as expected without additional boilerplate like:
>
> public function getSubstring (int $start, ?int $length = null): string
> {
> if ($this->isMultibyte) {
> return mb_substr($this->line, $start, $length,
> $this->encoding);
> } elseif ($length === null) {
> return substr($this->line, $start);
> } else {
> return substr($this->line, $start, $length);
> }
> }
>
> Or:
>
> public function getSubstring (int $start, ?int $length = null): string
> {
> if ($this->isMultibyte) {
> return mb_substr($this->line, $start, $length,
> $this->encoding);
> } else {
> return substr($this->line, $start, $length ??
> (strlen($this->line) - $start));
> }
> }
>
> Are there any historical reasons preventing substr() from accepting a null
> $length like mb_substr() does? I'd be happy to write the RFC and take a
> stab at the implementation if there's interest in such a change.
>
This is a fairly common deficiency in the implementation of internal
functions. Part of the reason is that historically zend_parse_parameters
did not support the ! modifier for integers, and partly these are just
implementation oversights.
Feel free to send a PR to fix this for PHP 8, no RFC needed. If you're
interested in addressing this for more functions, do a grep for "= UNKNOWN"
on the codebase, which gives you (with a few exceptions) a list of
functions that currently handle null parameters incorrectly and should
ideally be fixed for PHP 8.
Nikita
