如何在PHP重定向后显示警告框[关闭]

Well, the title's pretty self-explanatory. I have a form on an index.html.

And this PHP code to POST that form into an external URL and then redirect to the index again:

<?php

Echo "<style>body{background:#3e4744}</style>";
Echo "<style>h2{display:none}</style>";

//extract data from the post
//set POST variables
$url = 'https://blablabla.com';
$fields = array(
    'email' => urlencode($_POST['email'])
);

//url-ify the data for the POST
foreach($fields as $key=>$value) { $fields_string .= $key.'='.$value.'&'; }
rtrim($fields_string, '&');

//open connection
$ch = curl_init();

//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL, $url);
curl_setopt($ch,CURLOPT_POST, count($fields));
curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);

//execute post
$result = curl_exec($ch);

//close connection
curl_close($ch);

if (isset($_POST['submit'])){   
    ?>
    <script type="text/javascript">
        window.location = "/";
    </script>      
    <?php
}

?>

So, the thing is. How can I show an alert box saying something like: "Your post was succesfully sent" right after the page has been redirected?

As the index.html isn't processed on the server, you have to use some client side logic to transfer data from one page to the other. You could use session storage, local storage, cookies or just the url.

An easy way would be to just pass an indicator inside the url hash. To achieve this, you could modify your window.location like this

window.location = "/#success";

and inside the index.html just test, if the url hash is equal to #success

<script>
    if (window.location.hash == '#success') {
        alert('Success message..!');
    }
</script>