PHP OOP MySQL连接

Question

好吧，所以我是一个完全初学者在PHP的OOP，我想我会尝试一些简单的开始，但它不工作我期望的

<?php 

class mySQL{

  var $host;
  var $username;
  var $password;
  var $database;

  public function connect($set_host, $set_username, $set_password, $set_database){
    $this->host = $set_host;
    $this->username = $set_username;
    $this->password = $set_password;
    $this->database = $set_database;

    mysql_connect("$host", "$username", "$password")or die("cannot connect");
    mysql_select_db("$database")or die("cannot select DB");

  }

}

$connect = new mySQL();
$connect -> connect('localhost', 'user', 'pass', 'database1');

$settings_query = mysql_query("SELECT * FROM settings");
$settings = mysql_fetch_array($settings_query);

echo $settings['title']; 

?>

我得到的只是“无法连接”在我的页面上。

Answer 1

在您的connect方法中，您尝试使用以下变量：

• $host
• $username
• $password
• $database

这将是您的connect()方法的本地。
但那些变量不存在。

相反，如果要使用类中定义的属性 $host ， $username和$password ，则必须使用$this来访问它们 ：

• $this->host
• $this->username
• $this->password
• $this->database

有关更多信息，请查看PHP手册的此页面 - 您可能想要阅读有关类和对象的更多信息。

Answer 2

mysql_connect("$host", "$username", "$password")or die("cannot connect");

$host未在任何地方定义。 它需要是mysql_connect( $this->host, $this->username, $this->password ); 根据您自己的代码。

或许你只是复制粘贴mysql连接线？

Answer 3

class mySQL{

  var $host;
  var $username;
  var $password;
  var $database;
  public $dbh;  //Variable for storing connection

  public function connect($set_host, $set_username, $set_password, $set_database){
    $this->host = $set_host;
    $this->username = $set_username;
    $this->password = $set_password;
    $this->database = $set_database;

    $this->dbh = mysql_connect($this->host, $this->username, $this->password)or die("cannot connect"); //Store data connection specifier in object
    mysql_select_db($this->database)or die("cannot select DB");

  }

  public function query($sql)
  {
       return mysql_query($sql,$this->dbh);  //Specify connection handler when doing query
  }

  public function fetch($sql)
  {
       return mysql_fetch_array($this->query($sql));
  }

}
$connect = new mySQL();
$connect->connect('localhost', 'user', 'pass', 'database1');
$settings_query = mysql_query("SELECT * FROM settings", $connect->dbh); //Specify connection handler when doing query
$settings = mysql_fetch_array($settings_query);

//With query method in object you can do this:    
$settings_query = $connect->query("SELECT * FROM settings");  //Use object method to query
$settings = mysql_fetch_array($settings_query);

//with fetch method in object you can just do this:
$settings = $connect->fetch("SELECT * FROM settings");

echo $settings['title']; 

使用查询方法指定连接处理程序尤其简单，可以轻松地执行以下操作：

$connect1 = new MySQL();
$connect2 = new MySQL();
$connect1->connect('localhost','user','pass','database1');
$connect2->connect('localhost','user','pass','database2');

并且可以轻松地同时处理多个sql对象/数据库连接，并有助于缓解可能出现的任何混淆。

当然，除了正确引用其自身内的对象变量（ $this->var ）之外。

Answer 4

改成

mysql_connect( $this->host,  $this->username, $this->password)or die("cannot connect");

Answer 5

你可能想要$this ：

mysql_connect("{$this->host}", "{$this->username}", "{$this->password}")or die("cannot connect");
mysql_select_db("{$this->database}")or die("cannot select DB");

Answer 6

class mySQL{

  public function connect($set_host, $set_username, $set_password, $set_database){

    mysql_connect("$set_host", "$set_username", "$set_password")or die("cannot connect");
    mysql_select_db("$set_database")or die("cannot select DB");

  }

}

实际上这似乎对我来说很好..