php - 操作 MySQL 数据库数据

Question

我有一个 MySQL 数据库，其中包含列中的类列表，每个类都有一个“级别”，即行的值，它会因人而异。因此，例如，数学有 0、1、2 和 3 作为可能的值，0 未被选为类别，1、2 和 3 分别代表高、中和低。

我有一个 MySQL 查询，它只从用户的数据库行中提取类。

$result = mysql_query("SELECT math, physics, biology, chemistry, english, spanish, history, economics, art, theoryofknowledge, extendedessay FROM users WHERE username = '". $login_session ."'") or die(mysql_error());  

        while($row = mysql_fetch_array( $result )) {
            echo "Math:". $row['math'] ."<br />";
            echo "Physics:". $row['physics'] ."<br />";
            echo "Biology:". $row['biology'] ."<br />";
            echo "Chemistry:". $row['chemistry'] ."<br />";
            echo "English:". $row['english'] ."<br />";
            echo "Spanish:". $row['spanish'] ."<br />";
            echo "History:". $row['history'] ."<br />";
            echo "Economics:". $row['economics'] ."<br />";
            echo "Art:". $row['art'] ."<br />";
            echo "Theory of Knowledge:". $row['theoryofknowledge'] ."<br />";
            echo "Extended Essay:". $row['extendedessay'];
        }

这是用户的输出:

Math:1
Physics:1
Biology:0
Chemistry:2
English:2
Spanish:3
History:0
Economics:1
Art:0
Theory of Knowledge:1
Extended Essay:1

如果不在每次调用类时都执行 if 语句，我如何确定用户的级别？我需要在网站的多个位置调用类(class)，我想要一种简单的方法来检查用户有哪些类(class)和级别。

谢谢!

Answer 1

我认为最好的方法是构建一个 PHP 类，将用户加载到其中，并在其中包含一个可以接受类(生物学、数学等)并返回用户级别的函数。如果您愿意，您可以编写一些简单的代码来检查所需级别并根据用户级别是否足够高返回 true 或 false。

我什至拼凑了一些你可能想要扩展的 super 基本结构:

<?php

    class myUser
    // You are making an object here that stores information about your user.
    // This will mean you only need to query that data once from the DB, then
    // you can use it anywhere on the page without needing to do more queries.
    {
        public $math;
        public $biology;
        // I am making public variables here based on your columns
        // You cuold just as easily make an array for example to store them in.

        public function __construct($userID)
        // Making a construct class - meaning you will be able to write a snippet
        // like this: $currentUser = new myUser(6);
        // and the user information will be loaded nicely for you
        {
            $query="select math, biology from users where ID=$userID";
            // database stuff ....
            // this is where you would write your actual code to get the info
            // from the database and populate it properly, not like I did
            // below for this example
            $this->math=4;
            $this->biology=2;
        }

        public function checkUserLevel($myTopic, $reqLevel)
        // Making use of a few things here that I should ntoe:
        // This is a function you can call from the main code below
        // like this: $currentUser->checkUserLevel('math',3)
        // it will return either true or false.
        // I have used variable variables here for the $myTopic to
        // make it easier. You normally access an element differently
        // normally it is like: echo $this->math;  // output 4
        // Also I am using a ternary operator to return the data,
        // which is just a shortcut.
        {
            return ($this->$myTopic>=$reqLevel)? true : false;
        }

        public function returnUserLevel($myTopic)
        {
            return $this->$myTopic;
        }

    }

    $currentUser = new myUser(6);
    // This is creating a new user object based on the class we made above.
    // Further Explanation:
    // We have a class called myUser, but a class is just a schematic.
    // The $currenUser bit defines a new variable in our code.
    // the "= new myUser" bit says that we want to use the schematic above for this variable
    // the "myUser(6)" basically gives the constructor function an ID to get from
    // the database for the user. Because we defined a constructor class that expects
    // an ID, we need to supply it one, else we will get an error.
    // So $currentUser = new myUser(6)
    // really means "Make me a new variable called $currentUser and make it of the myUser
    // class type, and when making it, fetch me the details of student ID 6 and populate it
    // with their data.

    if($currentUser->checkUserLevel('math',3))
    // Now I am using one of the functions called checkUserLevel, supplying it
    // with the two arguments it needs and depending on it it returns true or false
    // doing one action or another.
    {
        echo "The user is at least level 3.\n";
    }
    else
    {
        echo "The user is lower than level 3.\n";
    }

    if($currentUser->checkUserLevel('biology',12))
    // same check, differnt inputs
    {
        echo "The user is at least level 3.\n";
    }
    else
    {
        echo "The user is lower than level 3.\n";
    }


    // You can output like this for example:
    echo "The users math is at: ".$currentUser->math;

    // and I added a little function that will simply return the level for you of the subject you enter.
    echo "The user is at math level ".$currentUser->returnUserLevel('math');

    // lastly you can do something like this:
    $allSubjects=array('math','physics','biology');
    for($i=0;$i<count($allSubjects);$i++)
    {
        echo "The users ".$allSubjects[$i]." level is at ".$currentUser->returnUserLevel($allSubjects[$i])."<br><br>";
    }

?>

代码的输出是:

The user is at least level 3.

The user is lower than level 3.