PHP and JavaScript, redirect url with alert message or confirm

In PHP, when we use header to redirect to a new url, we may find the alert message disappear. The following code will not show alert message:
<script>
          alert("User csv data is imported into publications database");
 </script>
<?php
header("Location: index.php");
?>

To solve this,
method 1:
we can use:
<?php
$message =  "User csv data is imported into publications database";
header("Location: index.php?message=" . urlencode($message));
?>
in index.php, add
if (isset($_GET['message'])) { echo  $_GET['message']; }




method 2: only using JavaScript
<script>
          alert("User csv data is imported into publications database");
          window.location.href ="../index.php" 
</script>

method 3: JavaScript with confirm yes or no
<script>
         if(confirm('Are you sure you want to redirect homepage?')) {location.href='index.php'};
   </script>

 Another Javscript redirection example, redirect to different websites via choose the option list
<select onchange="if(this.value!='') location.href='index.php?userid='+this.value">
          <option value=""> --- Choose a person --- </option>
           <option value="1"> Jiansen </option> 
            <option value="2"> Tom </option>  
            <option value="3"> Jerry </option>           
     </select>