如何使用php遍歷列中的所有行

Question

這是我的表數據和行

users     under_userid 
-------   ------------
demo        NULL  
user1       demo 
user2       user1 
user3       user1 
user4       user2

我試過如下查詢

$query = mysqli_query($con,"select under_userid from user where  users='user4'");    
$result = mysqli_fetch_array($query);
foreach ($result as $x => $x_value)
{            
  echo 'Value = ' . $x_value;      
}

我得到了上述語句的輸出

Value = user2

但我需要從輸出值中獲取所有 under_userid

Expected Output
 Value = user2
 Value = user1
 Value = demo

如何從輸出值中獲取所有 under_userid？
那么我需要使用 PHP 正確的 MySQL 查詢和循環語句嗎？

Answer 1

你需要一個遞歸函數：

function get_all_under($con, $userid) {
    $stmt = mysqli_prepare($con, "SELECT under_userid FROM user where user = ? AND under_userid IS NOT NULL");
    mysqli_stmt_bind_param($stmt, "s", $userid);
    mysqli_stmt_execute($stmt);
    mysqli_stmt_bind_result($stmt, $under_userid);
    $results = array();
    while (mysqli_stmt_fetch($stmt)) {
        echo "Value = $under_userid<br>";
        $results[] = $under_userid;
    }
    // Now get the next level
    foreach ($results as $under_userid) {
        get_all_under($con, $user_userid);
    }
}

get_all_under("user4");

Answer 2

將您的查詢替換為：

SELECT under_userid FROM user WHERE under_userid !=  'NULL'