require_once不PHP

Question

工作，如果我試圖在我的瀏覽器打開這個簡單的文件：

<?php 

require_once 'classes/settings.php'; 

class Mysql { 

    private $conn; 

    function __construct() { 

     $this->conn = new mysqli (DB_SERVER,DB_USER,DB_PASSWORD,DB_MEMBER) or die('There was a problem connecting to the database.'); 
     if ($this->conn->connect_errno) { 
echo "Failed to connect to MySQL: (" . $this->conn->connect_errno . ") " . $this->conn->connect_error; 
} 
//echo $mysqli->host_info . "\n"; 
    } 

    function verify_Username_and_Pass($un, $pwd) { 

     $query = "SELECT * 
     FROM users 
     WHERE username = ? AND password = ? 
     LIMIT 1"; 

     if($stmt = $this->conn->prepare($query)) { 

      $stmt->bind_param('ss',$un,$pwd); 
      $stmt->execute(); 

      if($stmt->fetch()) {  
       $stmt->close(); 
       return true; 
      } 
     } 
    } 
} 
?> 

我收到這樣的警告錯誤：

Warning: require_once(classes/settings.php): failed to open stream: No such file or 
directory in /var/www/classes/Mysql.php on line 3 Fatal error: require_once(): Failed 
opening required 'classes/settings.php' (include_path='.:/usr/share/php:/usr/share/pear') 
in /var/www/classes/Mysql.php on line 3 

我不明白爲什麼，在文件setting.php在該文件夾中，那麼問題是什麼？

---

編輯：

如果我這樣做，則這個與另一個文件，例如這樣的：

<?php 
require_once 'classes/settings.php'; 


$host = "localhost"; 
$user = "root"; 
$pass = "pass"; 

$databaseName = "membership"; 
$tableName = "users"; 

//-------------------------------------------------------------------------- 
// 1) Connect to mysql database 
//-------------------------------------------------------------------------- 

$con = mysql_connect($host,$user,$pass); 
$dbs = mysql_select_db($databaseName, $con); 

//-------------------------------------------------------------------------- 
// 2) Query database for data 
//-------------------------------------------------------------------------- 
$result = mysql_query("SELECT * FROM $tableName");   //query 
$array = mysql_fetch_row($result);       //fetch result  

//-------------------------------------------------------------------------- 
// 3) echo result as json 
//-------------------------------------------------------------------------- 
echo json_encode($array); 

?> 

這樣一來，它的工作原理沒有問題，我不明白爲什麼該文件和路徑是正確的，因爲在這第二部分代碼都工作。

Answer 1

既然你是已經在類文件夾，你有兩個選擇

第一種選擇是使用相對路徑

require_once 'settings.php';

第二個選項是使用絕對路徑

require_once $_SERVER['DOCUMENT_ROOT'] . '/classes/settings.php'

Answer 2

您的腳本var/www/classes/Mysql.php已經在的的classes目錄下。您包含的文件位於相同的目錄中。取出classes/和使用：

require_once 'settings.php'; 

Answer 3

嘗試使用$_SERVER['DOCUMENT_ROOT']

require_once ($_SERVER['DOCUMENT_ROOT'] . '/classes/settings.php');