PHP error message trigger ajax jquery displaying of error message - form validation

Question

I've done this before where if a field isn't filled out the PHP validation "echos" an error like this:

if(empty($_POST['formfield'])) {
echo "Error";
die();
} else {
    ...
}

then triggered a msg with jquery validation like this (this is pseudocode):

success: function(data) {
if (data=="Error") {
$("#Error").html('ERROR MSG HERE').show();
} else {
$("#Success").html('SUCCESS MSG HERE').show();
}

I have recently had to set up some pages with a simple log in for a vendor to download files. Again, this is simple!

<?php
$username = "foo";
$password = "bar";
if ($_POST['username'] != $username || $_POST['password'] != $password) {
?>
<!DOCTYPE>
<html>
<head></head>
<body>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" >
</body>
</html>
<?php
}
else {
?>
<!DOCTYPE>
<html>
<head></head>
<body>Logged in user sees this content</body>
</html>
<?php
}
?>

so my issue is this
I can't seem to figure out how to echo a message that will then trigger an error message on the form as I have done in the first 2 code blocks.

Obviously

<?php
$username = "foo";
$password = "bar";
if ($_POST['username'] != $username || $_POST['password'] != $password) {
**echo "Error";**
?>

just prints "Error" on page load. I need to figure out a way to simulate data being returned from the server - this form submits to itself - and show appropriate message (Username and/or Password are incorrect") if someone logs in with an incorrect username or password. I apologize for this being so long, and I truncated all the js stuff as I know it works. Thanks!

Cfreak · Accepted Answer · 2011-09-12 16:36:27Z

2

PHP is processed before Javascript. This gives you the ability to have PHP write out the Javascript that you want to display. Something like this should do what you want:

if ($_POST['username'] != $username || $_POST['password'] != $password) {
?>
<script>
$(document).ready(function() {

    $("#Error").html('ERROR MSG HERE').show();

});
</script>
<?php } ?>

answered Sep 12, 2011 at 16:36

Cfreak

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3 Comments

cwallenpoole Over a year ago

Just as a note: Make sure you put this in the HEAD or BODY tag.

Dirty Bird Design Over a year ago

@Cfreak - I'll give that a shot thanks! It will take some trial and error to integrate it with the other validation stuff. I'll see what I can come up with and post in pastebin. Thanks man

Dirty Bird Design Over a year ago

@Cfreak and cwalenpoole - I must be missing something. My PHP "validation" is above the doctype - If I output the JS with PHP in the body or head - how do I tie it into the condition that $username and or $password were incorrect?

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