[php-src] Issue #11434: "rtrim" function returns an empty string if the string contains "v".

Issue: https://github.com/php/php-src/issues/11434 Author: longfeiRen ### Description The following code: ```php <?php $str = 'vvv.ab'; echo rtrim($str, '.ab'),PHP_EOL; // echo "vvv" $str = 'vvv.vab'; echo rtrim($str, '.vab'),PHP_EOL; // echo "" $str = 'vvv.avab'; echo rtrim($str, '.avab'),PHP_EOL; // echo "" ``` Resulted in this output: ``` echo "vvv" echo "" echo "" ``` But I expected this output instead: ``` echo "vvv" echo "vvv" echo "vvv" ``` ### PHP Version php7.2/php8.1.11 ### Operating System _No response_