Php “错误”；不在对象上下文中使用$this“；有课

我有一门课是这样的：

<?php
    class DataConnection {

        private $hostName = "localhost";
        private $username = "root";
        private $password = "";
        private $dbName = "test";
        private $link = "";

        public function __construct() {

        }

        private function connect() {

            $this->link = mysql_connect($this->hostName, $this->username, $this->password)
                    or die ("Could not connect to the database");

            mysql_select_db($this->dbName, $this->link) or die("Could not select database");

        }

        // lay kieu du lieu cua record trong table
        public function getDataTypeTable($tableName) {

            $this->connect();// ERROR HERE

            $query = "SELECT * FROM {$tableName}";
            $result = mysql_query($query);

            $fields = mysql_num_fields($result);
            $rows   = mysql_num_rows($result);
            $table  = mysql_field_table($result, 0);
            echo "Your '" . $table . "' table has " . $fields . " fields and " . $rows . " record(s)\n";
            echo "The table has the following fields:\n";
            for ($i=0; $i < $fields; $i++) {
                $type  = mysql_field_type($result, $i);
                $name  = mysql_field_name($result, $i);
                $len   = mysql_field_len($result, $i);
                $flags = mysql_field_flags($result, $i);
                echo $type . " " . $name . " " . $len . " " . $flags . "\n";
            }

            //var_dump($results);

            //mysql_free_result($results);

        }

        public function __destruct() {
            mysql_close($this->link);
        }

    }
?>

---

如何调用
getDataTypeTable
？您可以将
connect（）
函数声明为静态函数，然后像
DataConnection:：connect（）
那样调用它，我认为它应该可以工作。真的很抱歉。我应该像$dataConnection->getDataTypeTable（“abc”）一样调用这个类；取而代之的是DataConnection:：getDataTypeTable（“abc”）@基勒黑尔：是的。您需要
->
。没有它，您将静态调用它，因此，
$this
不存在，因为您没有在实例上调用它。