From: jocrutrisi at ibsats dot com
Operating system: All
PHP version: 7.2.0RC1
Package: PCRE related
Bug Type: Bug
Bug description:PHP's PCRE API doesn't differentiate empty matches from non-matches
Description:
------------
PCRE differentiates "a sub-pattern that matched and is empty" from "a
sub-pattern that didn't match". But in PHP's exposed APIs both of these
cases produce a sub-pattern key with an empty match.
Probably this can be a flag, for unfortunate B.C. reasons, but the
current behavior is certainly not correct.
Test script:
---------------
$re = '%^
((?=x))?
((?=y))?
(\w)
$%mx';
$str = 'x
y
z';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Expected result:
----------------
Observe the identical PCRE regex and input on Regex101, notice the flag
"isParticipating" clearly points out which pattern matched (even if
empty) or didn't match:
[
[
{
"content": "x",
"isParticipating": true,
"groupNum": 0,
},
{
"content": "",
"isParticipating": true,
"groupNum": 1,
},
{
"content": "",
"isParticipating": false,
"groupNum": 2,
},
{
"content": "x",
"isParticipating": true,
"groupNum": 3,
}
],
[
{
"content": "y",
"isParticipating": true,
"groupNum": 0,
},
{
"content": "",
"isParticipating": false,
"groupNum": 1,
},
{
"content": "",
"isParticipating": true,
"groupNum": 2,
},
{
"content": "y",
"isParticipating": true,
"groupNum": 3,
}
],
[
{
"content": "z",
"isParticipating": true,
"groupNum": 0,
},
{
"content": "",
"isParticipating": false,
"groupNum": 1,
},
{
"content": "",
"isParticipating": false,
"groupNum": 2,
},
{
"content": "z",
"isParticipating": true,
"groupNum": 3,
}
]
]
Source: https://regex101.com/r/N90TJE/1
Actual result:
--------------
Both matching-and-empty and non-matching are just empty strings, we
can't tell them apart:
array(3) {
[0]=>
array(4) {
[0]=>
string(1) "x"
[1]=>
string(0) ""
[2]=>
string(0) ""
[3]=>
string(1) "x"
}
[1]=>
array(4) {
[0]=>
string(1) "y"
[1]=>
string(0) ""
[2]=>
string(0) ""
[3]=>
string(1) "y"
}
[2]=>
array(4) {
[0]=>
string(1) "z"
[1]=>
string(0) ""
[2]=>
string(0) ""
[3]=>
string(1) "z"
}
}
--
Edit bug report at https://bugs.php.net/bug.php?id=75181&edit=1
--
Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=75181&r=trysnapshot54
Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=75181&r=trysnapshot55
Try a snapshot (trunk): https://bugs.php.net/fix.php?id=75181&r=trysnapshottrunk
Fixed in SVN: https://bugs.php.net/fix.php?id=75181&r=fixed
Fixed in release: https://bugs.php.net/fix.php?id=75181&r=alreadyfixed
Need backtrace: https://bugs.php.net/fix.php?id=75181&r=needtrace
Need Reproduce Script: https://bugs.php.net/fix.php?id=75181&r=needscript
Try newer version: https://bugs.php.net/fix.php?id=75181&r=oldversion
Not developer issue: https://bugs.php.net/fix.php?id=75181&r=support
Expected behavior: https://bugs.php.net/fix.php?id=75181&r=notwrong
Not enough info: https://bugs.php.net/fix.php?id=75181&r=notenoughinfo
Submitted twice: https://bugs.php.net/fix.php?id=75181&r=submittedtwice
register_globals: https://bugs.php.net/fix.php?id=75181&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=75181&r=php4
Daylight Savings: https://bugs.php.net/fix.php?id=75181&r=dst
IIS Stability: https://bugs.php.net/fix.php?id=75181&r=isapi
Install GNU Sed: https://bugs.php.net/fix.php?id=75181&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=75181&r=float
No Zend Extensions: https://bugs.php.net/fix.php?id=75181&r=nozend
MySQL Configuration Error: https://bugs.php.net/fix.php?id=75181&r=mysqlcfg