Server-Side Scripting/Iteration/PHP

index.php

<?php

// Demonstrates conditions, while loops and for loops using
// Celsius and Fahrenheit temperature conversion tables.
//
// References:
//  https://www.mathsisfun.com/temperature-conversion.html
//  https://en.wikibooks.org/wiki/PHP_Programming
//  https://www.tutorialspoint.com/php/php_get_post.htm

$FORM = '
<h1>Temperature Conversion</h1>
<form method="POST">
<p><label for="start">Start:</label>
<input type="text" id="start" name="start" value="0"></p>
<p><label for="stop">Stop:</label>
<input type="text" id="stop" name="stop" value="100"></p>
<p><label for="increment:">Increment</label>
<input type="text" id="increment" name="increment" value="10"></p>
<p><input type="submit" name="submit" value="Celsius">
<input type="submit" name="submit" value="Fahrenheit"></p>
</form>
';

main();

function main() {
    switch($_SERVER["REQUEST_METHOD"]) {
        case "GET":
            echo $GLOBALS["FORM"];
            break;
        case "POST":
            $start = intval($_POST["start"]);
            $stop = intval($_POST["stop"]);
            $increment = intval($_POST["increment"]);
            $submit = $_POST["submit"];

            if ($submit == "Celsius") {
                echo process_celsius($start, $stop, $increment);
            }
            else if ($submit == "Fahrenheit") {
                echo process_fahrenheit($start, $stop, $increment);
            }
            else {
                echo "Unexpected submit value: " . submit;
            }
            break;
        default:
            echo "Unexpected request method:" . $_SERVER["REQUEST_METHOD"];
            break;
    } 
}

function process_celsius($start, $stop, $increment) {
    $result = "<h1>Temperature Conversion</h1>";
    $result = $result . "<table><tr><th>Celsius</th><th>Fahrenheit</th></tr>";
    $celsius = $start;
    while ($celsius <= $stop) {
        $fahrenheit = $celsius * 9 / 5 + 32;
        $result = $result . "<tr><td>" . $celsius . "</td>";
        $result = $result . "<td>" . number_format($fahrenheit, 1) . "</td></tr>";
        $celsius += $increment;
    }
    $result = $result . "</table>";
    return $result;
}

function process_fahrenheit($start, $stop, $increment) {
    $result = "<h1>Temperature Conversion</h1>";
    $result = $result . "<table><tr><th>Fahrenheit</th><th>Celsius</th></tr>";
    for ($fahrenheit = $start; $fahrenheit <= $stop; $fahrenheit += $increment) {
        $celsius = ($fahrenheit - 32) * 5 / 9;
        $result = $result . "<tr><td>" . $fahrenheit . "</td>";
        $result = $result . "<td>" . number_format($celsius, 1) . "</td></tr>";
    }
    $result = $result . "</table>";
    return $result;
}

?>

Try It

Copy and paste the code above into the following free online development environment or use your own PHP compiler / interpreter / IDE.

• PHPFiddle
• Repl.it