Help – self referenced form script not working

I am trying to use a contact form script, that references $PHP_SELF

I am using permalinks, and the form is not “finding itself”


<?
$form_block = "
<form method=\"post\" action=\"$PHP_SELF\">
Your name:<br>
<input type=\"text\" name=\"name\" size=30 value=\"$_POST[name]\"
Your email:<br>
<input type=\"text\" name=\"email\" value=\"$_POST[email]\"size=30
Comments:<br>
<textarea name=\"comments\" cols=30 rows=5 wrap=virtual>$_POST[comments]</textarea>
<input type=\"hidden\" name=\"op\" value=\"ds\">
<input type=\"submit\" name=\"submit\" value=\"Send Form\">
</form>";

if ($_POST[op] != "ds") {
echo "$form_block";

} else if ($_POST[op] =="ds") {

if ($_POST[name] == "") {
$name_err = "<font color=blue>Please enter your name!</font><br>";
$send="no";
}
if ($_POST[email] == "") {
$email_err = "<font color=blue>Please enter your email!</font><br>";
$send="no";
}
if ($_POST[comments] == "") {
$message_err = "<font color=blue>Please enter a comment!</font><br>";
$send="no";
}
if ($send !="no") {
$msg = "email sent from mywebsite.com\n";
$msg .="Name: $_POST[name]\n";
$msg .="Email: $_POST[email]\n";
$msg .="Comments: $_POST[comments]\n";
$to = "myname@mysite.com";
$subject = "Feedback Form";
$mailheaders = "From: My Website \n";
$mailheaders .= "Reply-To: $_POST[email]\n";
mail ($to, $subject, $msg, $mailheaders);
echo "Mail has been sent!";

} else if ($send == "no") {
echo "$name_err";
echo "$email_err";
echo "$message_err";
echo "$form_block";
}

}
?>