While using reserved PHP keywords as parameter name labels is allowed, in the context of function calls using named parameters in PHP 8.0+, this will easily lead to confusion. To avoid that, it is recommended not to use reserved keywords as function parameter names.
This commit renames the `$string` parameter to `$input_string` in:
* `POMO_Reader::substr()`
* `POMO_Reader::strlen()`
* `POMO_Reader::str_split()`
Follow-up to [52946], [52996], [52997], [52998], [53003], [53014], [53029], [53039], [53116], [53117], [53137], [53174], [53184], [53185], [53192], [53193], [53198], [53203], [53207], [53215], [53216], [53220], [53230], [53232], [53236], [53239], [53240], [53242], [53243], [53245], [53246], [53257], [53269], [53270], [53271], [53272], [53273], [53274], [53275], [53276], [53277], [53281], [53283], [53284], [53285], [53287], [53364], [53365], [54927], [54929], [54930], [54931], [54932], [54933], [54938], [54943], [54944], [54945], [54946], [54947], [54948], [54950], [54951], [54952], [54956], [54959].
Props jrf, aristath, poena, justinahinon, SergeyBiryukov.
See #56788.
Built from https://develop.svn.wordpress.org/trunk@54960
git-svn-id: http://core.svn.wordpress.org/trunk@54512 1a063a9b-81f0-0310-95a4-ce76da25c4cd
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