注意：未定義的變量：led_nem在C：上線71

Question

當我嘗試運行此查詢

$SQL = " SELECT * FROM info WHERE username = '$led_nem'"; 
$result = mysql_query($SQL); 
while ($db_field = mysql_fetch_assoc($result)) { 
     $tsk = $db_field['group_task']; 
} 

我得到這個錯誤\ XAMPP \ htdocs中\網絡\在線任務管理系統\ task_mem.php

注意：未定義的變量：led_nem在C：\ XAMPP \ htdocs中\網絡\在線 上線任務管理系統\ task_mem.php如果變量$led_nem存在71

Answer 1

測試使用前：

if (isset($led_nem)) { 
    $SQL = " SELECT * FROM info WHERE username = '$led_nem'"; 
    $result = mysql_query($SQL); 
    while ($db_field = mysql_fetch_assoc($result)) { 
     $tsk = $db_field['group_task']; 
    } 
} 

Answer 2

使用此

if (isset($led_nem)) { 
$SQL = " SELECT * FROM info WHERE username = '".$led_nem."'"; 
$result = mysql_query($SQL); 
while ($db_field = mysql_fetch_assoc($result)) { 
     $tsk = $db_field['group_task']; 
} 
}