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<?php preg_match('/b(?P<a>a)?/', 'xxxxbaxxxx', $matches); var_dump($matches); var_dump(array_key_exists('a', $matches));
Finding entry points
Branch analysis from position: 0
1 jumps found. (Code = 62) Position 1 = -2
filename:       /in/tgUG4
function name:  (null)
number of ops:  13
compiled vars:  !0 = $matches
line      #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
    3     0  E >   INIT_FCALL                                               'preg_match'
          1        SEND_VAL                                                 '%2Fb%28%3FP%3Ca%3Ea%29%3F%2F'
          2        SEND_VAL                                                 'xxxxbaxxxx'
          3        SEND_REF                                                 !0
          4        DO_ICALL                                                 
    5     5        INIT_FCALL                                               'var_dump'
          6        SEND_VAR                                                 !0
          7        DO_ICALL                                                 
    7     8        INIT_FCALL                                               'var_dump'
          9        ARRAY_KEY_EXISTS                                 ~3      'a', !0
         10        SEND_VAL                                                 ~3
         11        DO_ICALL                                                 
         12      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 8.0.0


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