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<?php $array = []; $array["a"] =& $array["b"]; $array["b"] = 1; var_dump($array);
Finding entry points
Branch analysis from position: 0
Jump found. (Code = 62) Position 1 = -2
filename:       /in/frbUc
function name:  (null)
number of ops:  11
compiled vars:  !0 = $array
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   3     0  E >   ASSIGN                                                   !0, <array>
   4     1        FETCH_DIM_W                                      $3      !0, 'b'
         2        CONT                                             $4      $3
         3        FETCH_DIM_W                                      $2      !0, 'a'
         4        ASSIGN_REF                                               $2, $4
   5     5        ASSIGN_DIM                                               !0, 'b'
         6        OP_DATA                                                  1
   6     7        INIT_FCALL                                               'var_dump'
         8        SEND_VAR                                                 !0
         9        DO_ICALL                                                 
        10      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 7.1.0