php - 无法从 PHP 访问数据库值

Question

我已从 php 连接到 mySql 数据库。我想从中获取两列的详细信息。当我尝试访问它们时，它输出 null。 当我在 phpmyAdmin 数据库工具中运行时，相同的查询字符串工作正常。

下面是我的代码:

$servername = "mysql";
            $username = "$$$$$$$$$";
            $password = "%%%%%%%%%%";
            $databasename = 'blog';

            // Create connection
            $conn = new mysqli($servername, $username, $password, $databasename);

            // Check connection
            if ($conn->connect_error) {
                die("Connection failed: " . $conn->connect_error);
            } else {
                echo "Connected successfully";
            }



 $select_sql = "Select site_url from sites where id LIKE '%website1Modal%'";
            $result = $conn->query($select_sql);

            if ($result->num_rows > 0) {
              echo "in if loop";
               echo $result[0];
}

上面的代码输出:“连接成功”和“在 if 循环中”。

有人可以告诉我我犯了什么愚蠢的错误吗？

Answer 1

if 不会让您陷入循环。 if 是一个控制结构。使用 while 进入循环并将 fetch 放入其中，以便可以访问结果。

尝试一下:

$servername = "mysql";
$username = "$$$$$$$$$";
$password = "%%%%%%%%%%";
$databasename = 'blog';
// Create connection
$conn = new mysqli($servername, $username, $password, $databasename);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} else {
    echo "Connected successfully";
}
$select_sql = "Select site_url from sites where id LIKE '%website1Modal%'";
$result = $conn->query($select_sql);
if ($result->num_rows > 0) {
    echo "in if control";
    while($row = $result->fetch_array()) { //this is optional; if only one row the while can be removed. e.g. $row = $result->fetch_array();
        echo 'in while loop';
        echo $row['site_url'];
    } //if removing while remove this as well
}

您可以在此处阅读有关 if 和 while 控件的更多信息。

http://php.net/manual/en/control-structures.if.php
http://php.net/manual/en/control-structures.while.php

这是 query 的手动输入确实如此。

重要的一点

For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object.

并且因为您有一个 mysqli_result 对象，您需要将其发送到 fetch这将

Returns an array of strings that corresponds to the fetched row or NULL if there are no more rows in resultset.