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<?php $test = ''; $test2 = null; echo is_null($test); echo is_null($test2);
Finding entry points
Branch analysis from position: 0
Jump found. Position 1 = -2
filename:       /in/YPvXJ
function name:  (null)
number of ops:  7
compiled vars:  !0 = $test, !1 = $test2
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   2     0  E >   ASSIGN                                                   !0, ''
   3     1        ASSIGN                                                   !1, null
   4     2        TYPE_CHECK                                    1  ~4      !0
         3        ECHO                                                     ~4
   5     4        TYPE_CHECK                                    1  ~5      !1
         5        ECHO                                                     ~5
         6      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 7.2.0