Bug #73913 [Nab->Opn]: broken strrpos with negative offset

Edit report at https://bugs.php.net/bug.php?id=73913&edit=1 ID: 73913 Updated by: heiglandreas@php.net Reported by: proartex at mail dot ru Summary: broken strrpos with negative offset -Status: Not a bug +Status: Open Type: Bug Package: Strings related Operating System: macOS Sierra 10.12.1 PHP Version: 5.6.29 Block user comment: N Private report: N New Comment: Looks like you're right! I dug deeper into it and it seems there is an issue when the negative offset is smaller or equals the size of the needle. I'm digging deeper into it. Previous Comments: ------------------------------------------------------------------------ [2017-01-11 18:03:34] proartex at mail dot ru 1. Does strrpos("works_like_a_charm", 'charm', 15) really equals to strrpos("works_like_a_charm", 'charm', -3)? false != 13. It is also applicable for 3 last cases. ------------------------------------------------------------------------ [2017-01-11 17:32:03] heiglandreas@php.net when offset is negative the search *starts* that many characters *from the end*. The search is not excluding the last n characters. strrpos("aaaa", 'aa', -2) == strrpos("aaaa", 'aa', 2) strrpos("aaaa", 'a', -1) == strrpos("aaaa", 'a', 3) strrpos("/documents/show/5474", '/', -20) == strrpos("/documents/show/5474", '/', 0) strrpos("works_like_a_charm", 'charm', -3) == strrpos("works_like_a_charm", 'charm', 15) strrpos("works_like_a_charm", 'charm', -4) == strrpos("works_like_a_charm", 'charm', 14) So they work as expected. What you want to do would be achieved by this: strrpos(substr("aaaa", -2), "aa"); When needle is longer than the remaining string, the offset seems to be expanded to at least include the needle. Note also the comment on http://php.net/manual/de/function.strrpos.php#76447 ------------------------------------------------------------------------ [2017-01-11 17:19:23] proartex at mail dot ru last case must be var_dump(strrpos("works_like_a_charm", 'charm', -5)); //ER: false, AR: 13 ------------------------------------------------------------------------ [2017-01-11 17:16:36] proartex at mail dot ru Description: ------------ It is seems broken at least in the following cases: - if negative offset equals to haystack length; - if negative offset less than needle length; - if needle length equals to (haystack length + negative offset) Negative offset should not move pointer but reduce search scope on the value of offset. In that case character placed at 0 position must not be found if search scope is reduced to empty string. Same should be applied in boundary cases: character placed next to reduced search scope must not be found (last case). Test script: --------------- <?php var_dump(strrpos("aaaa", 'aa', -2)); //ER: 0, AR: 2 var_dump(strrpos("aaaa", 'a', -1)); //ER: 2, AR: 3 var_dump(strrpos("/documents/show/5474", '/', -20)); //ER: false, AR: 0 var_dump(strrpos("works_like_a_charm", 'charm', -3)); //ER: false, AR: 13 var_dump(strrpos("works_like_a_charm", 'charm', -4)); //ER: false, AR: 13 Expected result: ---------------- 0 2 false false false Actual result: -------------- 2 3 0 13 13 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=73913&edit=1