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<?php $a = array(1, 2); $b = array(&$a); $a[] = $b; var_dump(json_encode($a), JSON_ERROR_SYNTAX); echo json_last_error();
Finding entry points
Branch analysis from position: 0
1 jumps found. (Code = 62) Position 1 = -2
filename:       /in/htQWf
function name:  (null)
number of ops:  16
compiled vars:  !0 = $a, !1 = $b
line      #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
    3     0  E >   ASSIGN                                                   !0, <array>
    4     1        INIT_ARRAY                                       ~3      !0
          2        ASSIGN                                                   !1, ~3
    5     3        ASSIGN_DIM                                               !0
          4        OP_DATA                                                  !1
    7     5        INIT_FCALL                                               'var_dump'
          6        INIT_FCALL                                               'json_encode'
          7        SEND_VAR                                                 !0
          8        DO_ICALL                                         $6      
          9        SEND_VAR                                                 $6
         10        SEND_VAL                                                 4
         11        DO_ICALL                                                 
    8    12        INIT_FCALL                                               'json_last_error'
         13        DO_ICALL                                         $8      
         14        ECHO                                                     $8
         15      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 8.0.0


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