PHP: Refresh page on invalid form submit

Question

How can I refresh a page with a form on submission pending the outcome of the submitted data and display a result.

e.g I have a page with a form:

<form action="" method="post">
   <input type="name" value="" name="name" placeholder="Your Name" />
   <input type="button" name="submit" value="submit form "/>
</form>

The engine that handles the form is external, but required in the page:

require_once 'form_engine.php';

form_engine.php checks the input,

$success = "true";
$errorMessage = " ";
$name = $_POST['name'];

if ( $name == '') {
      $errorMessage = 'Please enter your name';
      $success = false;
}
else (if $success = true) {
   // do something with the data

}

The form page contains the result:

<form action="" method="post">
   <input type="name" value="" name="name" placeholder="Your Name" />
   <input type="button" name="submit" value="submit form "/>
</form>
<p><?php echo $errorMessage; ?></p>

Will the error message get displayed after the form is submitted incorrectly? Or do I have to use a session to store it?

Answer 1

You need something like this:

if (!isset($_POST['name']))

instead of

if ( $name == 'name')

UPDATE

Try this, it should give you the idea:

<?php

    $errorMessage = false;

    if (isset($_POST['submit'])) {

        if (!isset($_POST['name']) || $_POST['name']=='') {
            $errorMessage = 'Please enter your name';
        }
        else {
           // do something with the data
           echo "Success!!";
        }
    }
?>

<form method="post">
   <input type="name" value="" name="name" placeholder="Your Name" />
   <input type="submit" name="submit" />
</form>
<p><?php if ($errorMessage) echo $errorMessage; ?></p>

Note: leaving out the action attribute will just submit the form to the current page

Note 2: The PHP here could very well be stored in another page. Using require() is the same as putting the code directly into the page.

Answer 2

You can use redirect on php side:

header('Location: www.mysite.com/index.php');