I am having problems figuring out how to retain users data when the validation fails. I am somewhat new to PHP so I might be making some huge mistakes in my logic. 

Currently if the validation fails all the fields are wiped clean and $\_Post data is also gone.

Here is some code assuming the user enters an invalid email I want the Name field to be retained. This code is not working.

```
<?php
if($_POST['doSubmit'] == 'Submit') {

   $usr_name = $data['Name'];
   $usr_email = $data['Email'];

   if (isEmail($usr_email)==FALSE){
       $err = "Email is invalid.");
       header("Location: index.php?msg=$err");
       exit();
    }

   //do whatever with data

}

if (isset($_GET['msg'])) {
   $msg = mysql_real_escape_string($_GET['msg']);
   echo "<div class=\"msg\">$msg</div><hr />";
}
if (isset ($_POST['Name'])){
   $reusername = $_POST['Name'];}
else{$reusername = "NOTHING";}//to test

 ?>
 <form action="index.php" method="post" >
 <input name="UserName" type="text" size="30" value="<?echo $reusername;?>">
 <input name="Email" type="text" size="30">
 <input name="doSubmit" type="submit" value="submit">
 </form>

 }

```