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<?php $regex = '/(((?!a).)*)*a\\{/'; $test_string = 'AAAAAAAAAAAAAA{AA'; echo mb_ereg_replace($regex,'WORKED',$test_string); echo "\n"; var_dump(preg_match($regex,$test_string));
Finding entry points
Branch analysis from position: 0
Jump found. Position 1 = -2
filename:       /in/0ZlIY
function name:  (null)
number of ops:  17
compiled vars:  !0 = $regex, !1 = $test_string
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   2     0  E >   ASSIGN                                                   !0, '%2F%28%28%28%3F%21a%29.%29%2A%29%2Aa%5C%7B%2F'
   3     1        ASSIGN                                                   !1, 'AAAAAAAAAAAAAA%7BAA'
   4     2        INIT_FCALL                                               'mb_ereg_replace'
         3        SEND_VAR                                                 !0
         4        SEND_VAL                                                 'WORKED'
         5        SEND_VAR                                                 !1
         6        DO_ICALL                                         $4      
         7        ECHO                                                     $4
   5     8        ECHO                                                     '%0A'
   6     9        INIT_FCALL                                               'var_dump'
        10        INIT_FCALL                                               'preg_match'
        11        SEND_VAR                                                 !0
        12        SEND_VAR                                                 !1
        13        DO_ICALL                                         $5      
        14        SEND_VAR                                                 $5
        15        DO_ICALL                                                 
        16      > RETURN                                                   1

Generated using Vulcan Logic Dumper, using php 7.2.0