Remove control characters from php String

Question

Hi all,

seems trivial but give me a hard time:

Does anyone have a hint for me on how to remove control characters like STX from a php string. I played around with

preg_replace("/[^a-zA-Z0-9 .\-_;!:?äÄöÖüÜß<>='\"]/","",$pString)

but found that it removed way to much. Is there a way to remove only controll chars?

tia

K

Answer 1

PHP does support POSIX-Classes so you can use [:cntrl:] instead of some fancy character-magic-stuff:

ereg_replace("[:cntrl:]", "", $pString);

Answer 2

If you mean by control characters the first 32 ascii characters and \x7F (that includes the carriage return, etc!), then this will work:

preg_replace('/[\x00-\x1F\x7F]/', '', $input);

(Note the single quotes: with double quotes the use of \x00 causes a parse error, somehow.)

The line feed and carriage return (often written \r and \n) may be saved from removal like so:

preg_replace('/[\x00-\x09\x0B\x0C\x0E-\x1F\x7F]/', '', $input);

I must say that I think Bobby's answer is better, in the sense that [:cntrl:] better conveys what the code does than [\x00-\x1F\x7F]. So, using ereg_replace instead of preg_replace:

ereg_replace('[:cntrl:]', '', $input);

Answer 3

regex free method

If you are only zapping the control characters I'm familiar with (those under 32 and 127), try this out:

 for($control = 0; $control < 32; $control++) {
     $pString = str_replace(chr($control), "", $pString;
 }

$pString = str_replace(chr(127), "", $pString;

The loop gets rid of all but DEL, which we just add to the end.

I'm thinking this will be a lot less stressful on you and the script then dealing with regex and the regex library.

Answer 4

its less stressful because ereg and ereg_replace are now depreceated

http://php.net/manual/en/function.ereg-replace.php