這種語法是錯誤的嗎？

Question

我在我db.php中

define("DB_USER","root"); 
define("DB_PASSWORD",""); 
define("DB_DB","exotic_live"); 
define("DB_HOST", "localhost"); 

定義此拋出一個錯誤

Parse error: syntax error, unexpected T_STRING, expecting T_FUNCTION in C:\xampp\htdocs\test\config\db.php on line 5

完整的代碼是

class Database{ 

//define('DB_HOST','localhost'); 
define("DB_USER","root"); 
define("DB_PASSWORD",""); 
define("DB_DB","exotic_live"); 
define("DB_HOST", "localhost"); 

private function db_connect(){ 
$this->dbconnect(); 
} 

    private function dbconnect() { 
    $conn = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD) 
     or die ("<br/>Could not connect to MySQL server"); 

    mysql_select_db(DB_DB,$conn) 
     or die ("<br/>Could not select the indicated database"); 

    return $conn; 
    } 
} 

$obj_db=new Database(); 
$obj_db->db_connect(); 

Answer 1

常量是全局常量，而define() s不能在一個類定義出現（除非他們是在它的方法）。

類常量的定義是這樣的：

const DB_USER = "root"; 
const DB_PASSWORD = ""; 
const DB_DB = "exotic_live"; 
const DB_HOST = "localhost"; 

而在相同類中引用的這樣的：

private function dbconnect() { 
    $conn = mysql_connect(self::DB_HOST, self::DB_USER, self::DB_PASSWORD) 
     or die ("<br/>Could not connect to MySQL server"); 

    mysql_select_db(self::DB_DB,$conn) 
     or die ("<br/>Could not select the indicated database"); 

    return $conn; 
    } 

和類外引用與Database::代替self::（如靜態成員）。

Answer 2

你不能把一個define禮類的聲明中。把他們與define()取得

//define('DB_HOST','localhost'); 
define("DB_USER","root"); 
define("DB_PASSWORD",""); 
define("DB_DB","exotic_live"); 
define("DB_HOST", "localhost"); 


class Database{ 
[...] 
} 

Answer 3

您不能在類定義中定義常量。

外線定義它們，或者將它們定義爲class constants.

Answer 4

要在類中定義常量使用以下語法：

class Foo { 
    const Bar = 'value'; 
}