PHP Security - $_POST - Injection
<?
if ($_POST['submit']=="1"){

    $input = $_POST['input'];
    echo "echo the input: ".$input."<br/>";
}
?>
<form action="<? $PHP_SELF;?>" method="POST">
<input type="text" name="input" value="<? echo $_POST['input'];?>"/>
<input type="hidden" name="submit" value="1"/>
<input type="submit" value="submit"/>
</form>

";unset('index.php');