undefined index error message

[kronch]

I keep getting this error when I test-run my file:

Notice: Undefined index: operation in c:\inetpub\wwwroot\completeForm.php on line 26

I know that I can turn down the error-reporting level in the ini file, but that doesn't tell me why I'm getting the error in the first place... Here's the code I've written (following an example):

if ($POST['operation'] != "doSomething") {
//they need to see the form
echo "$formBlock";
} else if ($POST['operation'] == "doSomething"){
if ($_POST['senderName'] == "") {
$nameError = "<font color=\"red\">Please enter your NAME!</font><br>";
$send = "no";
}

It's the very first line that is causing the error - no other error messages appear...

[LordShryku]

That means that the value isn't set. Use isset() to check first

if(isset($_POST['operation'])) {
   if($_POST['operation'] != "doSomething") {
      //they need to see the form
      echo $formBlock;
   } 
   else {
      if($_POST['senderName'] == "") {
         $nameError = "<font color=\"red\">Please enter your NAME!</font><br>";
         $send = "no";
      }
   }
}