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<?php $strings = ["folders/folder1/folder5/../../folder2", "folders/folder1/../../../folder2", "folders/folder1/folder5/../folder2"]; foreach ($strings as $url) { echo preg_replace('~(?<=/|^)(?!\.\.(?![^/]))[^/\n]+/(?R)?\.\.(?:/|$)~', '', $url) . PHP_EOL; }
Finding entry points
Branch analysis from position: 0
2 jumps found. (Code = 77) Position 1 = 2, Position 2 = 11
Branch analysis from position: 2
2 jumps found. (Code = 78) Position 1 = 3, Position 2 = 11
Branch analysis from position: 3
1 jumps found. (Code = 42) Position 1 = 2
Branch analysis from position: 2
Branch analysis from position: 11
1 jumps found. (Code = 62) Position 1 = -2
Branch analysis from position: 11
filename:       /in/41NKW
function name:  (null)
number of ops:  13
compiled vars:  !0 = $strings, !1 = $url
line      #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
    3     0  E >   ASSIGN                                                   !0, <array>
    4     1      > FE_RESET_R                                       $3      !0, ->11
          2    > > FE_FETCH_R                                               $3, !1, ->11
    5     3    >   INIT_FCALL                                               'preg_replace'
          4        SEND_VAL                                                 '%7E%28%3F%3C%3D%2F%7C%5E%29%28%3F%21%5C.%5C.%28%3F%21%5B%5E%2F%5D%29%29%5B%5E%2F%5Cn%5D%2B%2F%28%3FR%29%3F%5C.%5C.%28%3F%3A%2F%7C%24%29%7E'
          5        SEND_VAL                                                 ''
          6        SEND_VAR                                                 !1
          7        DO_ICALL                                         $4      
          8        CONCAT                                           ~5      $4, '%0A'
          9        ECHO                                                     ~5
    4    10      > JMP                                                      ->2
         11    >   FE_FREE                                                  $3
    6    12      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 8.0.0


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