php - 在 php 中检索 mysql 数据并回显检索到的数据

Question

    <?php
    $username = "root";
    $password = "password";
    $database = "xxxxxx";
    $link = mysql_connect("localhost", $username, $password);    
     $query = "SELECT rollno FROM users where username = '".$_SESSION['MM_Username']."'";
    mysql_select_db('xxxxxx', $link);
     $result = mysql_query($query) or die(mysql_error($link));
     $num = mysql_num_rows($result);
     mysql_close();

  $rows = array();

  $result = mysql_query($query) or die(mysql_error());
  $rows = array();
  while($r = mysql_fetch_row($result))
  {
   $rows[] = $r[0];
   }
   print_r($rows); 
   ?>

这是我的代码，我想显示当前登录用户的卷号和当我运行此代码时，我没有选择数据库。

Answer 1

首先，您应该正确编码，这意味着数据库连接和数据库选择应该位于顶部:

<?php
    $username = "root";
    $password = "password";
    $database = "xxxx";
    $link = mysql_connect("localhost", $username, $password);
    mysql_select_db('xxxx', $link);

    $query = "SELECT rollno FROM users where username = '".$_SESSION['MM_Username']."'";
    $result = mysql_query($query) or die(mysql_error($link));
    $num = mysql_num_rows($result);

    $rows = array();
    $result = mysql_query($query) or die(mysql_error());
    $rows = array();
    while($r = mysql_fetch_row($result))
    {
        $rows[] = $r[0];
    }

    print_r($rows);
    mysql_close();
   ?>

最后还移动了mysql_close();
另一个要点是，现在 mysql_ 已弃用，请使用 mysqli_