not sure why I am getting an undefined variable error

[webguync]

Hi, I am testing out some simple code while trying out PHP OOP to connect to the MySQL DB. I am getting an undefined variable error, but not sure why.

 

the test code is:

<?PHP
error_reporting(E_ALL);
 include('includes/db.php');
 $db = new db();


 $db->query("SELECT title FROM blog_posts WHERE id = '7'");
 if($sql)
 {
	  while($r = mysql_fetch_array($sql))
	  {
		   echo $r['title'];
		   
	  }
 }
?>

 

and the code to connect to the DB is:

<?PHP
class db
{
 private $hostname;
 private $username;
 private $password;
 private $database;
 private $connect;
 private $select_db;

 public function db()
 {
	  $this->hostname = "";
	  $this->username = "";
	  $this->password = "";
	  $this->database = "";
 }

 public function open_connection()
 {
	  try
	  {
		   $this->connect = mysql_connect($this->hostname,$this->username,$this->password);
		   $this->select_db = mysql_select_db($this->database);
	  }
	  catch(exception $e)
	  {
		   return $e;
	  }
 }

 public function close_connection()
 {
	  try
	  {
		   mysql_close($this->connect);
	  }
	  catch(exception $e)
	  {
		   return $e;
	  }
 }

 public function query($sql)
 {
	  try
	  {
		   $this->open_connection();
		   $sql = mysql_query($sql);
	  }
	  catch(exception $e)
	  {
		   return $e;
	  }
	  $this->close_connection();
	  return $sql;
 }
}
?>

 

the specific error is...

 

Undefined variable: sql in E:\DBTest.php on line 9

[BlueSkyIS]

because $sql is not defined, it is not set to anything. you need to define it using the return value from the function, something like this:

 

$sql = $db->query("SELECT title FROM blog_posts WHERE id = '7'");
if($sql)
// etc.

[webguync]

ah yes, makes sense. That was easy enough, thx!