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<?php $subusers = [" hey", " h i", " ", "wh@t"]; foreach ($subusers as $subuser) { echo "Assess \"$subuser\":\t"; if (!strlen($subuser = trim($subuser))) { echo "* Username not entered"; } elseif (!ctype_alnum($subuser)) { echo "* Username not alphanumeric"; } echo "\n"; }
based on cqQiW
Finding entry points
Branch analysis from position: 0
2 jumps found. (Code = 77) Position 1 = 2, Position 2 = 24
Branch analysis from position: 2
2 jumps found. (Code = 78) Position 1 = 3, Position 2 = 24
Branch analysis from position: 3
2 jumps found. (Code = 43) Position 1 = 14, Position 2 = 16
Branch analysis from position: 14
1 jumps found. (Code = 42) Position 1 = 22
Branch analysis from position: 22
1 jumps found. (Code = 42) Position 1 = 2
Branch analysis from position: 2
Branch analysis from position: 16
2 jumps found. (Code = 43) Position 1 = 21, Position 2 = 22
Branch analysis from position: 21
1 jumps found. (Code = 42) Position 1 = 2
Branch analysis from position: 2
Branch analysis from position: 22
Branch analysis from position: 24
1 jumps found. (Code = 62) Position 1 = -2
Branch analysis from position: 24
filename:       /in/MF7SZ
function name:  (null)
number of ops:  26
compiled vars:  !0 = $subusers, !1 = $subuser
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   2     0  E >   QM_ASSIGN                                                !0
   3     1      > FE_RESET_R                                       $3      !0, ->24
         2    > > FE_FETCH_R                                               $3, !1, ->24
   4     3    >   ROPE_INIT                                     3  ~5      'Assess+%22'
         4        ROPE_ADD                                      1  ~5      ~5, !1
         5        ROPE_END                                      2  ~4      ~5, '%22%3A%09'
         6        ASSIGN_OBJ                                               ~4
   5     7        INIT_FCALL                                               'trim'
         8        SEND_VAR                                                 !1
         9        DO_ICALL                                         $7      
        10        QM_ASSIGN                                        $8      !1
        11        STRLEN                                           ~9      $8
        12        BOOL_XOR                                         ~10     ~9
        13      > JMPZ                                                     ~10, ->16
   6    14    >   ASSIGN_OBJ                                               '%2A+Username+not+entered'
        15      > JMP                                                      ->22
   7    16    >   INIT_FCALL                                               'ctype_alnum'
        17        SEND_VAR                                                 !1
        18        DO_ICALL                                         $11     
        19        BOOL_XOR                                         ~12     $11
        20      > JMPZ                                                     ~12, ->22
   8    21    >   ASSIGN_OBJ                                               '%2A+Username+not+alphanumeric'
  10    22    >   ASSIGN_OBJ                                               '%0A'
   3    23      > JMP                                                      ->2
        24    >   FE_FREE                                                  $3
  11    25      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 7.4.0