Is to store a magic value in the session and in a hidden form field. On submit, the session value is removed. If the session value is missing, nothing gets posted. 

That is. 

Or manually kill the $POST vars after submission maybe.... ? 

It's amazing and sad how many people seem to click yes without thinking though. I hope they don't do that for java applets.
To be fair, that's what happens when too many things ask too many stupid questions. You condition people to click YES out of reflex. 

You may already have tried this, or already have this. But, try putting "exit;" after your header("Location: ") redirect. 

Can't post anywhere 

 

not sure why it can happen, but this means you loaded the page with one IP address, but when you submitted your post you had a different IP.

Maybe it happens on mobile phones more because they can change networks frequently? (edge <-> 3g <-> wifi) 

I understand. I'm at home where I'm in my wifi, but sometimes it switches to mobile broadband for some reason. Thanks! 

i can see how that might help, as my php still generates the entire page after you post.

I wonder if chrome is ignoring the redirect because it's the same URL? In that case i could use a second URL as the post target and then redirect back to view_thread.php. 

Seems it's a chrome bug: https://code.google.com/p/chromium/issues/detail?id=177855&q=reload&colspec=ID%20Pri%20Mstone%20ReleaseBlock%20OS%20Area%20Feature%20Status%20Owner%20Summary

Will be fixed soon judging by my skim of that report. 

i'll just do nothing then :)

(though adding an "exit" to my php after the redirect still sounds like a good idea to save server resources) 

Although it's a bug and that it's being addressed, it's still too late.

Not many people will bother to upgrade their Chrome to latest version--we've seen that habit with IE users.

Simply adding several lines of javascript, and you'll be able to convert your "Post A Reply" < form > to use Ajax.

By looking at your HTML code, I can see that you are using javascript without any libraries such as mootools, jquery, etc. -- which is fine, you can still do ajax with plain javascript.

---

Just adjust your HTML slightly by adding an ID to the <td> that holds the "Post A Reply" form html.
Currently it is:
< td bgcolor="#333333" width="500" valign="top" >
< span class="header2">Post A Reply:</span >
...
< /td >

Change the < td > to have id="post-a-reply"
So, you then have < td bgcolor="#333333" width="500" valign="top" id="post-a-reply" >

Then, the javascript would be:

On submit:

var xmlhttp;
if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else { // code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
document.getElementById("post-a-reply").innerHTML = xmlhttp.responseText;
}
}
xmlhttp.open("POST","http://celephais.net/board/view_thread.php?id=2&start=1676&ajax=1",true);
xmlhttp.send();

---

Notice I added another parameter "&ajax=1" to the submit URL, and you can use that in PHP to spit out a specific response for the update to the < td >, rather spit the entire page as if there was no ajax.

Obviously the "id=2&start=1676" part is dynamic, of course. 

Hmm, that one line got garbled. It changed my quotation character to "&quo..." Let's try again:

xmlhttp.open("POST", "http://celephais.net/board/view_thread.php?id=2&start=1676&ajax=1" ,true);


Ahhh, whatever. 

Chrome updates automatically. 

Deqer, this is a veey change-averse group ;-) 

Still doesn't hurt to add some ajax to the site. Ajax has been available and supported for 10+ years now. Saves on resources, too.

It's 2013. Get with it. 

Please don't. Javascript is bloody annoying. 

Please don't, and it's not necessary at all. You can protect against double posts entirely on the server. 

Please don't. Javascript is bloody annoying.

uhm.. javascript is used already? 

I do have plans for ajax, in fact it's already used for the "flag spam" feature that moderators have. But this site is not my active project right now (aside from necessary maintenance.)And don't worry, I would only use it for enhancements that make sense for the design of the site. 

Yeah, better not let a stranger like me tell you how to improve your outdated website. Best you figure it out on your own. Maybe another 10 years, and you'll come around. 

if you are not listening to the many people who give you helpful advice, then why should they listen to you. 

He's gone critical! He's gonna blow!

I knew it wouldn't last. Awesome. 

Welcome to the OLD SKOOL!!!