Warning: Undefined array key "user_id" in C:\xampp\htdocs\PEC_old\HopDong\list_hd.php on line 7

Fatal error: Uncaught mysqli_sql_exception: Unknown column 'tbl_hopdong.user_id' in 'where clause' in C:\xampp\htdocs\PEC_old\HopDong\list_hd.php:15 Stack trace: #0 C:\xampp\htdocs\PEC_old\HopDong\list_hd.php(15): mysqli->query('SELECT * FROM t...') #1 {main} thrown in C:\xampp\htdocs\PEC_old\HopDong\list_hd.php on line 15