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<?php $number = 1; $answer = "p__v_"; $letter = mb_substr( $answer , 2, 1 ); $answer = preg_replace('/'.$letter.'/u', '_',$answer,1); echo $answer;
Finding entry points
Branch analysis from position: 0
1 jumps found. (Code = 62) Position 1 = -2
filename:       /in/2G3M2
function name:  (null)
number of ops:  19
compiled vars:  !0 = $number, !1 = $answer, !2 = $letter
line      #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
    2     0  E >   ASSIGN                                                   !0, 1
    3     1        ASSIGN                                                   !1, 'p__v_'
    4     2        INIT_FCALL                                               'mb_substr'
          3        SEND_VAR                                                 !1
          4        SEND_VAL                                                 2
          5        SEND_VAL                                                 1
          6        DO_ICALL                                         $5      
          7        ASSIGN                                                   !2, $5
    5     8        INIT_FCALL                                               'preg_replace'
          9        CONCAT                                           ~7      '%2F', !2
         10        CONCAT                                           ~8      ~7, '%2Fu'
         11        SEND_VAL                                                 ~8
         12        SEND_VAL                                                 '_'
         13        SEND_VAR                                                 !1
         14        SEND_VAL                                                 1
         15        DO_ICALL                                         $9      
         16        ASSIGN                                                   !1, $9
    7    17        ECHO                                                     !1
         18      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 8.0.0


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