Create Simple Calculator in PHP

So, in this application I am using two input HTML TextBoxes for entering operands for calculations, a button for the calculation and a drop down list for selecting an operator, and a button for the calculation. In it is simply a HTML TextBox value, in other words operand value and also an operator value is accepted in this way:

$_REQUEST['name']

In that way you can simply store the TextBox value or drop down list value for calculation in a PHP variable. I handle lost of errors in this script. I am simply checking that the TextBox value is empty or not using:

if($_REQUEST['fvalue']==NULL && $_REQUEST['lvalue']==NULL)

If an error exists then an alert is shown with a message depending on the error.
 
The following is the calculator code:

<?php

ini_set('display_errors',0);

if( isset( $_REQUEST['calculate'] ))

{

$operator=$_REQUEST['operator'];

if($operator=="+")

{

$add1 = $_REQUEST['fvalue'];

$add2 = $_REQUEST['lvalue'];

$res= $add1+$add2;

}

if($operator=="-")

{

$add1 = $_REQUEST['fvalue'];

$add2 = $_REQUEST['lvalue'];

$res= $add1-$add2;

}

if($operator=="*")

{

$add1 = $_REQUEST['fvalue'];

$add2 = $_REQUEST['lvalue'];

$res =$add1*$add2;

}

if($operator=="/")

{

$add1 = $_REQUEST['fvalue'];

$add2 = $_REQUEST['lvalue'];

$res= $add1/$add2;

}

if($_REQUEST['fvalue']==NULL && $_REQUEST['lvalue']==NULL)

{

echo "<script language=javascript> alert(\"Please Enter values.\");</script>";

}

else if($_REQUEST['fvalue']==NULL)

{

echo "<script language=javascript> alert(\"Please Enter First value.\");</script>";

}

else if($_REQUEST['lvalue']==NULL)

{

echo "<script language=javascript> alert(\"Please Enter second value.\");</script>";

}

}

?>

<form>

<table style="border:groove #00FF99">

            <tr>

                <td style="background-color:aqua; color:red; font-family:'Times New Roman'">Enter First Number</td>

                <td colspan="1">

               

                    <input name="fvalue" type="text" style="color:red"/></td>

            <tr>

                <td style="color:burlywood; font-family:'Times New Roman'">Select Operator</td>

                <td>

                    <select name="operator" style="width: 63px">

<option>+</option>

<option>-</option>

<option>*</option>

<option>/</option>

</select></td>

               </tr>

            <tr>

                <td style="background-color:aqua; color:red; font-family:'Times New Roman'">Enter First Number</td>

                <td class="auto-style5">

                    <input name="lvalue" type="text"  style="color:red"/></td>

               

            </tr>

            <tr>

                <td></td>

                <td><input type="submit" name="calculate" value="Calculate" style="color:wheat;background-color:rosybrown" /></td>

               

            </tr>

            <tr>

                <td style="background-color:aqua;color:red">Output = </td>

                <td style="color:darkblue"><?php echo $res;?></td>

               

            </tr>

       </table>

 </form>

Output

What is the Difference Between get , post and request method ?

21DEC

In HTML to transfer records from one page to another page , attribute method is used in form tag.

i.e :

<form method="post" action="action.php">
data goes here .......
</form>

Now , In this case action.php is destination page where user will have records .

in PHP : there are 3 methods to retrieve data from receiving page.

1 ) $_GET

2) $_POST

3) R_REQUEST

$_GET :

$_GET is a super global array which is an inbuilt array. Which collects values from a form sent with method=”get” as well it collects values from URL also. ( e.g. http://www.domainname.com/pagename.php?data=123)

You can print $_GET with inbuilt function in php i.e ( print_r($_GET) ).

IMP : Information sent from this method will be visible in ( address bar of any browser ) and has limitation on characters .

As per W3C Community limitation can be extended up to 4000 characters

Myth: Search services will not index anything with a “?” in the URI.

Myth: URIs cannot be longer than 256 characters

for details : visit : About $_GET limitation :

You can read more details about $_GET.

$_POST :

$_POST is a super global array which is an inbuilt array. Which collects values from a form sent with method=”post”.

You can print $_GET with inbuilt function in php i.e ( print_r($_POST)  ).

IMP : Information received from POST method is always invisible in ( address bar of any browser ) . It has more limit on sending characters to action page.

This limitation can be set in php.ini file

Note: We can change by setting the POST_MAX_SIZE in the php.ini file . by default we will find this value with 8MB in most of the php.ini file.

$_REQUEST :

$_REQUEST is a super global array which is an inbuilt array. Which collects values from a form sent with  either method=”post” or method=”get” .

You can print $_REQUEST with inbuilt function in php i.e ( print_r($_REQUEST)  ).

IMP : One of the best way of getting data on action page , here we did not require to check that which method we have used to pass data from sending page.Even $_REQUEST get records from the COOKIE also.