Form

i created form i need that i can Add to number or Subtract user choose what to do (+ or -)
how to correct form ,can i do this in end form with + or -:
<div>
<?php

if(isset($_POST["userSelected"])){
$nm = $_POST["userSelected"];
//echo $nm ;
if($nm != ""){
$number = $user_pass[$nm];
//echo $number;
$txtErr = "<form action='$Iam' method='post'>";
$txtErr .= "<p> Name <input name='nm' value='" . $nm . "'></p>";
$txtErr .= "<p> Number <input name='num' value='" . $number . "'></p>";

$txtErr .= "<p><input type='submit' value='Submit' name='Submit'></p></form>";
} else {
$txtErr = "choose name";
}
}
?>
</div>

 

Your question makes no sense, your code is a laundry list of how NOT to write php including a bit of "security, what's that"...

Could you better explain what you are trying to accomplish and what form your post data is coming from?