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<?php $foo; $bar = 2; echo($foo ?? $bar); echo((isset($foo) && $foo !== null) ? $foo : $bar);
based on 2XBJ2
Finding entry points
Branch analysis from position: 0
Jump found. Position 1 = 6, Position 2 = 8
Branch analysis from position: 6
Jump found. Position 1 = 9, Position 2 = 11
Branch analysis from position: 9
Jump found. Position 1 = 12
Branch analysis from position: 12
Jump found. Position 1 = -2
Branch analysis from position: 11
Jump found. Position 1 = -2
Branch analysis from position: 8
filename:       /in/YrQq7
function name:  (null)
number of ops:  14
compiled vars:  !0 = $foo, !1 = $bar
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   3     0  E >   ASSIGN                                                   !1, 2
   4     1        COALESCE                                         ~3      !0
         2        QM_ASSIGN                                        ~3      !1
         3        ECHO                                                     ~3
   5     4        ISSET_ISEMPTY_VAR                           310378496  ~4      !0
         5      > JMPZ_EX                                          ~4      ~4, ->8
         6    >   IS_NOT_IDENTICAL                                 ~5      !0, null
         7        BOOL                                             ~4      ~5
         8    > > JMPZ                                                     ~4, ->11
         9    >   QM_ASSIGN                                        ~6      !0
        10      > JMP                                                      ->12
        11    >   QM_ASSIGN                                        ~6      !1
        12    >   ECHO                                                     ~6
        13      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 7.1.0