Victor’s Programming Aid

So you have successfully created a PHP class and want access to the classes variables and functions. As a reminder to programming beginners, you can only access public variables and public functions. That is a function or variable that was declared with the public keyword or no keyword (as PHP functions and variables are by default public). Below is a quick refresher example where functionNumberOne and functionNumberTwo are public and functionNumberThree is private.

class Common {
   public $secondVariable = "2";
   private $thirdVariable = "3";

   function functionNumberOne() {
      echo "This is my first function";
   }

   public function functionNumberTwo() {
      echo "This is my second function";
   }

   private function functionNumberThree() {
      echo "This is my third function";
   }
}

If the class is declared in another a separate file, remember to first include the file before your first attempt to access the class. Generally, the best place to include files is at the very top of the file.

Assuming our Common class function above, our first step to accessing our PHP variables and functions is to create an object. In programming terms, this is known as initializing an object instance. To create the class instance:

$myInstance = new Common();

How was the previous code snippet generated? You can choose any name to replace the $myInstance variable (so long as it is not a keyword). Next, new is a PHP keyword that in this situation signifies the creation of a new object. Finally, Common() is constructed by using the class name (in this case Common) followed by an open parenthesis and close parenthesis ‘()‘. If you have a specified a constructor, make sure you include the correct number of parameters.

Finally, to access the public variables we use the $myInstance object followed by ‘->’ and the public variable or function name. When accessing the variable name, you do not need to start with $. Again, we have a code example below.

echo $myInstance->secondVariable;
$myInstance->functionNumberOne();
$myInstance->functionNumberTwo();

And there we have it. You now have access to public PHP functions and PHP variables. Note that the use of classes is a new feature to PHP 5.

Round trip database reads becomes an issue with large databases. You may notice this occurs in grid views. Each time the dataset is sorted or filtered, the default grid view needs to be data binded. In most cases, the data source is the database (sql statement or stored procedure). An easy way to prevent these round trips across page loads is to use a session variable. One important aspect to note is that session variables expire by default after fifteen minutes.

We are going to store a Boolean variable rememberMe in a ViewState. By storing the Boolean in a ViewState, rememberMe will retain its value across page loads. In this example, the boolean variable rememberMe will default to false. The variable rememberMe can be read to and from as if any public class variable.

public partial class _Default : System.Web.UI.Page
{
  public bool rememberMe
  {
    get
    {
      object o = ViewState["rememberMe "];
      return (o == null)? false : (bool)o;
    }
    set
    {
      ViewState["rememberMe"] = value;
    }
  }

  protected void Page_Load(object sender, EventArgs e)
  {

  }

}

Again, it is important to note that session variables expire by default after fifteen minutes. If a default value is not assigned, additional logic is required to prevent unanticipated affects. This method is very effective when retrieving an extremely large number of records. You will immediately notice the first query will take the standard query time, but each subsequent action on the same dataset will be very quick.