在执行PHP之前如何弹出JavaScript确认窗口？

Question

How to popup a JavaScript confirmation window before executing:

<form action="index.php" method="get">
  <input type="hidden" name="act" value="run">
  <input type="submit" value="Clear map">
</form>
<?php
  if (!empty($_GET['act'])) {
        mysql_query("TRUNCATE TABLE mapinfo");
        $page = $_SERVER['PHP_SELF'];
        header("Location: $page");
  } 
?>

User has to press OK to execute PHP or Cancel to not.

Answer 1

<?php
  // mysql connection
  if ($_GET['act'] == 'run') {
        mysql_query("TRUNCATE TABLE mapinfo");
        $page = $_SERVER['PHP_SELF'];
        header("Location: $page"); // for this to work, script must not output something before, otherwise use echo '<script type="text/javascript">window.location = \''.$page.'\';</script>';
        die;
  } 
?>
<form action="index.php" method="get" onsubmit="return confirm('Are you sure you want to truncate `mapinfo`?');">
  <input type="hidden" name="act" value="run">
  <input type="submit" value="Clear map">
</form>

Answer 2

Use javascript confirm() to do so. Add an onclick attribute to the submit button that will call a confirm dialog and check with javascript if option yes then some code and if not then some other code.

Answer 3

PHP script is evaluated on the server, before the site is sent to the client. The javascript is evaluated only when the client starts processing the page. So you cant really do anything in javascript before the php script is evaluated.

A solution would be to set up a proxy page that handle the javascript stuff you need, and then refer you to the php page.

Hope that helps!

Answer 4

试试这一行，

<a href="truncate_page.php" onclick="return confirm('Are you sure you want to truncate?')">Truncate</a>