Try this
index.html
<form action="form.php" method="post">
Do you like stackoverflow?
<input type="checkbox" name="like" value="Yes" />
<input type="submit" name="formSubmit" value="Submit" />
</form>
form.php
<html>
<head>
</head>
<body>
<?php
if(isset($_POST['like']))
{
echo "<h1>You like Stackoverflow.<h1>";
}
else
{
echo "<h1>You don't like Stackoverflow.</h1>";
}
?>
</body>
</html>
Or this
<?php
if(isset($_POST['like'])) &&
$_POST['like'] == 'Yes')
{
echo "You like Stackoverflow.";
}
else
{
echo "You don't like Stackoverflow.";
}
?>