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<?php preg_match('/(?<foo>y)?x(?<bar>y)?/', 'x', $matches); print_r($matches); preg_match('/(?<foo>y)?()x(?<bar>y)?/', 'x', $matches); print_r($matches);
Finding entry points
Branch analysis from position: 0
1 jumps found. (Code = 62) Position 1 = -2
filename:       /in/ra13Q
function name:  (null)
number of ops:  17
compiled vars:  !0 = $matches
line      #* E I O op                               fetch          ext  return  operands
-----------------------------------------------------------------------------------------
    3     0  E >   INIT_FCALL                                                   'preg_match'
          1        SEND_VAL                                                     '%2F%28%3F%3Cfoo%3Ey%29%3Fx%28%3F%3Cbar%3Ey%29%3F%2F'
          2        SEND_VAL                                                     'x'
          3        SEND_REF                                                     !0
          4        DO_ICALL                                                     
    4     5        INIT_FCALL                                                   'print_r'
          6        SEND_VAR                                                     !0
          7        DO_ICALL                                                     
    6     8        INIT_FCALL                                                   'preg_match'
          9        SEND_VAL                                                     '%2F%28%3F%3Cfoo%3Ey%29%3F%28%29x%28%3F%3Cbar%3Ey%29%3F%2F'
         10        SEND_VAL                                                     'x'
         11        SEND_REF                                                     !0
         12        DO_ICALL                                                     
    7    13        INIT_FCALL                                                   'print_r'
         14        SEND_VAR                                                     !0
         15        DO_ICALL                                                     
         16      > RETURN                                                       1

Generated using Vulcan Logic Dumper, using php 8.5.0


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