How to fix “The URI you submitted has disallowed characters” error.

Does this screenshot look familiar?

codeigniter 400 error for disallowed characters

Well, it has been killing me for the last 2 hours. I have encountered this error before, but I never realized what caused it, or how it was fixed. I would just try random stuff, entering in different content, moving different functions. Eventually it would go away…


In this situation, whenever I would click on a particular link I got the error. I copied and pasted the URL from the browser into Sublime Text. It looked like this:


What the heck? I never added those characters. They never showed in the browser URL, and trying to replace them in my code was not working.

I tried editing the entries in my database in order to remove the character. I deleted and edited each field. I even tried converting the character encoding and trimming the URL. Nothing worked!

I then read a post on the PyroCMS Forum that said there is probably a hidden character somewhere in the code. Well, I looked in my PHP and I didn’t find anything, looking in my HTML there was nothing there either.

So what to do? When in doubt, use vim. I dusted off my vim and looked at the PHP file, nothing! Then I opened the HTML file…

HEY! There is a tiny little hidden character in my HTML!!

The Fix

I removed the character and everything worked perfectly. Here is the diff after I removed the character:

git diff for hidden character

You can see there is a little trailing character there. I don’t know exactly how this got in there, but god damn was it driving me crazy.

In Summation

The real problem is, this didn’t show in Sublime Text or in the Chrome elements panel. Even the commit on Github didn’t show the hidden character I removed.

github diff for hidden character

The only way it would show up is when I opened the file in vim!