모든세션변수삭제 세션ID : 14ja4g75ceu2e5crttjc5vj9je
session1 :
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session2 :
Warning: Undefined array key "session2" in /users/2018/i1858067/public_html/2019/webprog/ch10/exam10-07.php on line 14

session3 :
Warning: Undefined array key "session3" in /users/2018/i1858067/public_html/2019/webprog/ch10/exam10-07.php on line 15

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