Question

连接文件是：

$DBconnect = mysqli_connect("localhost", "root", "", "project" );

这适用于除了一个之外的所有页面，这会产生此错误：未定义的变量：DBconnect

这部分：

include_once('connection.php');
// Function that will convert a user id into their username
function getusername($uid) {

$res = mysqli_query($DBconnect, "SELECT username FROM users WHERE id='".$uid."' LIMIT 1") or die(mysql_error());

感谢您的建议

Answer 1

更改此

    function getusername($uid){
$res = mysqli_query($DBconnect, "SELECT username FROM users WHERE id='".$uid."' LIMIT 1") or die(mysql_error());
}

到这个

    function getusername($uid){
    global $DBconnect;
    $res = mysqli_query($DBconnect, "SELECT username FROM users WHERE id='".$uid."' LIMIT 1") or die(mysql_error());
    }

或

function getusername($uid,$DBconnect){
        $res = mysqli_query($DBconnect, "SELECT username FROM users WHERE id='".$uid."' LIMIT 1") or die(mysql_error());
        }

Answer 2

这是一个范围问题。

$DBConnect在全局范围内可用，但您无法自动访问函数中的全局范围。所以将$DBConnect作为参数传递给函数，一切都很好。

include_once('connection.php');

function getusername($uid, $DBConnect) {

    $res = mysqli_query($DBconnect, "SELECT username 
                                     FROM users 
                                     WHERE id='$uid' LIMIT 1"); 
    if ( ! $res ) {
       echo mysql_error();
       exit;
    }

}

// call function with an extra parameter i.e. the $DBConnect

getusername($uid, $DBConnect);

仅在一个页面上找不到数据库连接变量

2 个答案: