PHP 8 shows a warning on routes with dynamic variables

[juhana]

On routes that have dynamic, non-regex variables (e.g. /foo/:id) there's a warning on PHP 8.1 about passing null to substr:

Deprecated: substr(): Passing null to parameter #1 ($string) of type string is deprecated in vendor/shardj/zf1-future/library/Zend/Controller/Router/Route.php on line 288

The line is this:

zf1-future/library/Zend/Controller/Router/Route.php

Line 288 in 9a10c63

if (substr($part, 0, 2) === '@@') {

It should be:

if ($part !== null && substr($part, 0, 2) === '@@') { 

$part can be null at that point as mentioned on line 96 ("stores [its] regex requirement or null") and there's already another null check later on line 298, so it's not a case of an invalid route or other configuration issue.

[alexkuusk]

if (substr($part ?? '', 0, 2) === '@@') {
would also work

[alexgit2k]

Or

$part = $this->_parts[$pos] ?? '';

instead of

zf1-future/library/Zend/Controller/Router/Route.php

Line 273 in 9a10c63

$part = $this->_parts[$pos];

[alexgit2k]

$part = $this->_parts[$pos] ?? ''; does not work, because there is a check for $part !== null afterwards.
Used the solution of juhana which is already used in the same way a few lines below.