Bug #73948 [Dup]: Preg_match_all should return empty strings on optional capture groups.

Edit report at https://bugs.php.net/bug.php?id=73948&edit=1 ID: 73948 Updated by: nikic@php.net Reported by: tomasyorke at hotmail dot com Summary: Preg_match_all should return empty strings on optional capture groups. Status: Duplicate Type: Bug Package: PCRE related Operating System: Windows 7 PHP Version: 7.0.14 Block user comment: N Private report: N New Comment: Not sure if it's quite a duplicate. IIRC we now use null instead of "" if unmatched, but we still don't fill up null values at the end. Previous Comments: ------------------------------------------------------------------------ [2017-01-16 14:38:08] requinix@php.net Duplicate of bug #61780, fixed in master. (unmatched groups will be NULL) ------------------------------------------------------------------------ [2017-01-16 14:24:55] tomasyorke at hotmail dot com Description: ------------ Using preg_match_all with the PREG_SET_ORDER flag and an optional capture group might return either an empty string or a missing element. This depends on whether there is a matched capture group after the non-matched capture group. From an interface perspective, this means that I have to check for two representations to test whether an optional capture group was matched. The test script demonstrates such a case. When considering a fix, the first priority should be that whatever the representation is (NULL, an empty string or a missing element.), it should be consistent, no matter if there is a matched capture group after or not. If this cannot be fixed due to backwards compatibility Issues. Could we add a PREG_KEEP_NONMATCHES or PREG_SET_ORDER_2 flag? Test script: --------------- <?php preg_match_all("#(a)?(b)(c)?#","b",$matches,PREG_SET_ORDER); var_dump($matches); Expected result: ---------------- array(1) { [0] => array(3) { [0] => string(1) "b" [1] => string(0) "" [2] => string(1) "b" [3] => string(0) "" } } Actual result: -------------- array(1) { [0] => array(3) { [0] => string(1) "b" [1] => string(0) "" [2] => string(1) "b" } } ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=73948&edit=1