An Example Program

So let’s look at how a real life PHP program integrates with an HTML form by creating the program convert.php listed in Following Example. Type it in as shown and try it for yourself.

<?php // convert.php
$f = $c = "";
if (isset($_POST['f'])) $f = sanitizeString($_POST['f']);
if (isset($_POST['c'])) $c = sanitizeString($_POST['c']);
if ($f != '')
{
	$c = intval((5 / 9) * ($f - 32));
	$out = "$f °f equals $c °c";
}
elseif($c != '')
{
	$f = intval((9 / 5) * $c + 32);
	$out = "$c °c equals $f °f";
}
else $out = "";
echo <<<_END
<html><head><title>Temperature Converter</title>
</head><body><pre>
Enter either Fahrenheit or Celsius and click on Convert
<b>$out</b>
<form method="post" action="convert.php">
Fahrenheit <input type="text" name="f" size="7" />
Celsius <input type="text" name="c" size="7" />
<input type="submit" value="Convert" />
</form></pre></body></html>
_END;
function sanitizeString($var)
{
	$var = stripslashes($var);
	$var = htmlentities($var);
	$var = strip_tags($var);
	return $var;
}
?>