Question

在我的Android应用中。我正在尝试对用户进行身份验证，因为我已经编写了一个php脚本来建立与数据库的连接，但不幸的是我收到了以下错误 -

＆＃34;未定义的变量：con \ wamp \ www \ android_connect \ db_connect.php 48 ＆＃34;

要解决此错误，我已将 ＆＃34; $ con＆＃34; 声明为全局变量，但仍会出现相同的错误 -

我的 db_connect.php 代码是---

<?php

/**
 * A class file to connect to database
 */
class DB_CONNECT 
{

    private $con;    

    // constructor
    function __construct() 
    {
        // connecting to database
        $this->connect();
    }

    // destructor
    function __destruct() 
    {
        // closing db connection
        $this->close();
    }

    /**
     * Function to connect with database
     */
    function connect() 
    {
        // import database connection variables
        require_once __DIR__ . '/db_config.php';

        // Connecting to mysql database             
    $con = mysqli_connect(DB_SERVER, DB_USER, DB_PASSWORD, DB_DATABASE);

        // Selecing database
        $db = mysqli_select_db($con, DB_DATABASE); 
        // returing connection cursor
        return $con;
    }

   /*       
    * Function to close db connection
    */
    function close() 
    {
    // closing db connection
        mysqli_close($con);

    }   
}

?>

请帮助。谢谢..！

Answer 1

<?php

/**
 * A class file to connect to database
 */
class DB_CONNECT 
{

    private $con;    

    // constructor
    function __construct() 
    {
        // connecting to database
        $this->connect();
    }

    // destructor
    function __destruct() 
    {
        // closing db connection
        $this->close();
    }

    /**
     * Function to connect with database
     */
    function connect() 
    {
        // import database connection variables
        require_once __DIR__ . '/db_config.php';

        // Connecting to mysql database             
        $this->con = mysqli_connect(DB_SERVER, DB_USER, DB_PASSWORD, DB_DATABASE);

        // Selecing database
        $db = mysqli_select_db($this->con, DB_DATABASE); 

        // returing connection cursor
        return $this->con;
    }

    /*       
     * Function to close db connection
     */
    function close() 
    {
        // closing db connection
        mysqli_close($this->con);
    }   
}

?>

使用$this->con代替$con，因为$con是一个类变量，并且您将其用作本地变量。

Answer 2

问题 - 函数$con中的connect()变量未将$con的值赋给您给出的公共变量，同样地，在close()函数中它没有引用公共变量。

将您的功能连接更改为 -

function connect() 
    {
        // import database connection variables
        require_once __DIR__ . '/db_config.php';

        // Connecting to mysql database             
    $this->con = mysqli_connect(DB_SERVER, DB_USER, DB_PASSWORD, DB_DATABASE);

        // Selecing database
        $db = mysqli_select_db($con, DB_DATABASE); 
        // returing connection cursor
        return $con;
    }

和函数close（）as -

function close() 
    {
    // closing db connection
        mysqli_close($this->con);

    }

最终守则 -

<?php

/**
 * A class file to connect to database
 */
class DB_CONNECT 
{

    private $con;    

    // constructor
    function __construct() 
    {
        // connecting to database
        $this->connect();
    }

    // destructor
    function __destruct() 
    {
        // closing db connection
        $this->close();
    }

    /**
     * Function to connect with database
     */
    function connect() 
    {
        // import database connection variables
        require_once __DIR__ . '/db_config.php';

        // Connecting to mysql database             
    $this->con = mysqli_connect(DB_SERVER, DB_USER, DB_PASSWORD, DB_DATABASE);

        // Selecing database
        $db = mysqli_select_db($con, DB_DATABASE); 
        // returing connection cursor
        return $con;
    }

   /*       
    * Function to close db connection
    */
    function close() 
    {
    // closing db connection
        mysqli_close($this->con);

    }   
}

?>

未定义的变量：在<i> 48 </i>的C：\ wamp \ www \ android_connect \ db_connect.php中的con

2 个答案: