Re: Check a string does not contain invalid characters

John Comerford wrote:

Hi Folks, I am new to php. I want to accept a character string which I will use as a unique user id. I want to check the string to ensure the user has not typed characters that I consider to be invalid as part of a user id. I was thinking of doing something along the lines of: if (strpbrk($userid, '~!@#$%^&*()_+=-{}[]\\|;\':"<>?,./`') <> null) { blah, blah, blah......

it is always better to know what you want to allow and only allow those. this will catch anything that is not a letter of the alphabet. if ( preg_match('!^[^a-zA-Z]+$!', $userid) == 1 ) { die('Found something other then a letter.'); } if ( preg_match('!^[^a-zA-Z0-9]+$!', $userid) == 1 ) { die('Found something other then a number or letter.'); } this returns an (int) either 0 or 1 0 = it did not match anything 1 = it matched at least on char that is invalid. check out the function here http://us2.php.net/preg_match check out its big brother http://us2.php.net/preg_match_all The big difference is that preg_match will only look until it finds the first match, then it stops looking and returns. preg_match_all finds all possible matches in the input string. Jim

but I think that would still leave me open to control characters. I am thinking maybe I should loop through the string character by character and check it's ascii value (using ord) is within the range of a-z and A-Z ? Is this the best way of achieving this ? Is there a php command to do something similar ? I have done a few web searches and haven't come up with much. TIA, JC