从数据库中读取单个值并将其保存在变量中 - Read single value from database and save it in variable

Read single value from database and save it in variable

我的数据库中有一个小表，看起来像这样:

----------------------
id | name      | value
----------------------
1  | test.flag | 0
----------------------
2  | username  | franz
----------------------

我只是尝试读取test.flag的值并将结果存储在一个变量中。

<?php
    $servername = "127.0.0.1";
    $username   = "test";
    $password   = "test123";
    $dbname     = "testdb";
    $conn = mysqli_connect($servername, $username, $password, $dbname);
    if (!$conn)
    { 
        die("Connection to database failed with error#: " . mysqli_connect_error()); 
    }   
    $sql = "SELECT value FROM mytable WHERE name='test.flag';";
    $result = mysqli_query($conn, $sql);
    echo "<p>".$result."</p><br>";
    if (mysqli_query($conn, $sql))
    {
        echo "<p>Sucessfully</p><br>";
    } else {
        echo "Error: " . $sql . "<br>" . mysqli_error($conn);
    }
    echo "<p>".$sql."</p><br>";
?>

但是在我执行这个script.php文件后，它加载了一个空白页面。

您需要获取行，然后echo。

$result = mysqli_query($conn, $sql);
$row = mysqli_fetch_assoc($result);
echo "Result: " . $row['value'];

查询的值不存储在$sql变量中。

像@user5173426回答，你必须先获取它。

示例(http://www.w3schools.com/php/php_mysql_select.asp):

while($row = $result->fetch_assoc())
   $toEcho = $row["value"];
echo $toEcho;