PHP Class Example

By Sergey Skudaev

In this tutorial you will learn a little about Object Oriented Programming in PHP. I will not write about theory or history of Object Oriented Programming. You can find it in Wikipedia . I give you just one simple example that helps you to understand the concept. First, I give you a simple code example in procedural style, then the same code example with using functions and then the same example with using a class. (OOP approach).

Let us create a simple form that allows us to enter two numbers and a simple PHP code that calculate sum of the numbers, its difference, its multiplication and division.

<html>
<head>
</head>
</body>
<form method="post" action="calc_procedural_code.php">
<table>
<tr><td><input type="text" name="number1" size="10"></td></tr>
 <tr><td><input type="text" name="number2" size="10"></td></tr>
<tr><td><input type="submit" name="submit" value="Calculate"></td></tr>
</table>

</form>
</body>
</html>

Save form as calculator.html file. Now let us write PHP code that performs the calculation.

<?
//calc_procedural_code.php
$num1=$_POST['number1'];
$num2=$_POST['number2'];

$sum=$num1 + $num2;
$difference=$num1 - $num2;
$multi=$num1 * $num2;
$div=$num1/$num2;

echo "Sum=".$sum." <br>";
echo "Difference =".$difference." <br>";
echo "Multilpication=".$multi." <br>";
echo "Division=".$div."<br>";

?>

Save file as calc_procedural_code.php. Run the calculator.html form on a web server and enter any numbers like 6 and 3. Click the calculate button. The PHP script will display output:

Sum = 9

Difference = 3

Multilpication = 18

Division = 2

Let us perform the same calculation by using functions in PHP code. Create file "calc_function.php" with the following code:

<?

//Define functions for each calculation action

function add($number1, $number2) {
        $sum=$number1 + $number2;
return $sum;
    }

function subtract($number1, $number2) {

$dif=$number1 - $number2;
return $dif;

}

function multiply($number1, $number2) {

$multi=$number1 * $number2;
return $multi;
}

function divide($number1, $number2) {

$dev=$number1/$number2;
return $dev;
}

$num1=$_POST['number1'];
   $num2=$_POST['number2'];

//call functions:
$sum=add($num1, $num2);
$dif= subtract($num1, $num2);
$multi= multiply($num1, $num2);
$div= divide($num1, $num2);

//Output the result

echo "Sum=".$sum." <br>";
echo "Difference =".$dif." <br>";
echo "Multilpication=".$multi." <br>";
echo "Division=".$div."<br>";
?>

Edit calculator.html file. Change action="cacl_procedural_code.php" to action="calc_function.php" Again, run the calculator.html form on a web server and enter any numbers like 6 and 3. Click the calculate button. The PHP script will display output:

Sum = 9

Difference = 3

Multilpication = 18

Division = 2

Now let us create PHP code with class.


<?

// define class
class Calculator {
//class variables:
var $sum;
var $dif;
var $multi;
var $div;
//Class member functions or methods:
       function add($number1, $number2) {
         $this->sum=$number1 + $number2;
      }
     function substract($number1, $number2) {
         $this->dif=$number1 - $number2;
     }

     function multiply($number1, $number2) {
         $this->multi=$number1 * $number2;
     }

     function devide($number1, $number2) {
         $this->div=$number1/$number2;
     }

}

$num1=$_POST['number1'];
$num2=$_POST['number2'];

//Create a class instance:
$calc = new Calculator();

//Call class methods:
$calc->add($num1,$num2);
$calc->substract($num1,$num2);
$calc->multiply($num1,$num2);
$calc->devide($num1,$num2);

//Display output:

echo "Sum=".$calc->sum." <br>";
echo "Difference =".$calc->dif." <br>";
echo "Multilpication=".$calc->multi." <br>";
echo "Division=".$calc->div."<br>";
?>

Save file as calc_class.php. Edit calculator.html form and type action="calc_class.php". Run the calculator.html form, enter numbers and click Calculate button. The calculation result will display on the next page.

We are done.

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