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<?php $false = "a"; $v = true; echo (string) ${!$v}, PHP_EOL; echo !isset(${!$v});
Finding entry points
Branch analysis from position: 0
1 jumps found. (Code = 62) Position 1 = -2
filename:       /in/8j971
function name:  (null)
number of ops:  12
compiled vars:  !0 = $false, !1 = $v
line      #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
    3     0  E >   ASSIGN                                                   !0, 'a'
    4     1        ASSIGN                                                   !1, <true>
    5     2        BOOL_NOT                                         ~4      !1
          3        FETCH_R                      local               ~5      ~4
          4        CAST                                          6  ~6      ~5
          5        ECHO                                                     ~6
          6        ECHO                                                     '%0A'
    6     7        BOOL_NOT                                         ~7      !1
          8        ISSET_ISEMPTY_VAR                             4  ~8      ~7
          9        BOOL_NOT                                         ~9      ~8
         10        ECHO                                                     ~9
         11      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 8.0.0


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