php remove unknown characters

Question

I am building a web application which will run in electron with angular as a frontend framework and laravel as a backend framework. In the application it's possible to login with a smartcard (thanks to node-pcsclite), it reads the bytes on the smartcard and then I convert them.

The smartcard contains a code which is linked to the staff table in my MSSQL database. I can retrieve the code from the smartcard and I can log into the application when it uses mysql as database server.

Now when I'm trying to do the same but with mssql, I get an error which should be viewed in html mode instead of the error page itself.

(The code can be alphanumeric)

So it adds all these strange characters (probably non-existing characters), not that much of a problem right? At least, that's what I thought. So I tried to fix it by using this code inside my laravel controller:

preg_replace('/[^A-Za-z0-9\-]/', '', $string);

This didn't solve anything. Then I thought I might have a problem with the query, so I ran SQL Profiler, the problem is that (probably because of the special characters) the query is broken.

select top 1 * from [Staff] where [CodeInit] = '
go

So does anyone know how to really remove the strange characters?

If you need more information feel free to ask.

I assume you have obfuscated the string deliberately with asterisks? The value that is now mainly asterisks - is it encased with quote marks because it doesn't look like it in the screenshot? — Professor Abronsius, Aug 14 '15 at 07:48
First of all, these red characters aren't asterisks, those are dots (probably because it can't display what it really is). If I take a look at the error page, it displays this query: SQL: select top 1 * from [Staff] where [CodeInit] = 10741. The problem is that the dots are illegal characters but I can't remove them. — Stefan, Aug 14 '15 at 07:51
Have you tried something like this? http://stackoverflow.com/questions/1176904/php-how-to-remove-all-non-printable-characters-in-a-string — Millard, Aug 14 '15 at 08:01
It got fixed, it was my fault, I was using the function in the wrong place. Excuse me. — Stefan, Aug 14 '15 at 08:36

score -1 · Answer 1 · answered May 30 '16 at 14:11

I had this problem and landed to this question when searching for a solution. I was unable to find any fix.

The string with non-printable characters retrieved from mdecrypt_generic() so I wanted a way to remove those characters. When I copy and paste the retrieved value from browser to Brackets text editor, it show these red dots.

I just pasted it to google and then it was encoded to %10. Nothing helped till now, so as a temporary solution I just used rtrim() to remove those dots.

Copy the dot in brackets and replace with "DOT_HERE".

rtrim(rtrim($pvp, "DOT_HERE"), "\0\4");

"\0\4" will remove only nulls and EOT but not that dot character(%10).

Further here is a screenshot with that red dot. You can use Brackets text editor to see this.

Note that $pvp is the decrypted text.

php remove unknown characters

1 Answers1