php mysql_select_db not working

Question

我创建了一个名为'class.admin.php'的类，它做了一些检查。我有一个文件，调用类的工作很好，直到它试图选择db.

当我运行mysql_select_db() or die时，我得到错误'No database selected'。

class.admin.php

class admin {
    ### Function that check for the connect file (if it exists)
    public function checkConnector() {
        if(file_exists(CONN)) { return true; } else { return false; }
    }
    ### Check connection to MYSQL
    public function checkConnection() {
        global $cn; if(mysql_connect()) { return true; } else { return false; }
    }
    ### Check connection to database
    public function checkDB() { 
        global $db; if(mysql_select_db()) { return true; } else { return false; } 
    }

index . php

$admin = new admin();
# Check the connect file exists
if($admin->checkConnector() === true) {
    # Check connection to MYSQL server
    if($admin->checkConnection()  === true) {
        ### Check selection of DB
        if($admin->checkDB() === true) {
            print 'Selection of database is fine.';
        } else {
            print 'Selection of database is not working.';
        }
    } else {
        print '<p>I'm sorry, could not connect to MYSQL.</p>';
    };
} else {
    print '<p>I'm sorry the connection file does not exist. Please install accordingly.</p>';
}

Answer 1

对于SELECT a DB，您必须提供其名称

mysql_select_db();   // wrong, which database to select?

正确

mysql_select_db("MyDatabaseName"); 

参考:mysql_select_db