用户输入验证仅允许数字和字母

Question

I have a form where users enter in car registrations so I only want to allow numbers and letters?

if(preg_match("/(A-Za-z0-9]+/", $to)){

$errors[] = "Only use numbers and letters please";}

get the error...

Warning: preg_match() [function.preg-match]: Compilation failed: missing ) at offset 12 in /homepages/28/d420353834/htdocs/regupdate.php on line 84

So I am guessing I have got it wrong.

Answer 1

Try:

if(preg_match("/([A-Za-z0-9])+/", $to)){
    // action ...       
}

You're missing [ at start and at the end ) in regexp

Answer 2

You're missing [ before the A , and a ) before the final / in your regex. Should look like:

if (preg_match("/([A-Za-z0-9]+)/", $to)) {

Also, if you're only testing for boolean, and not collecting the matches, you could omit the () entirely.

Answer 3

改为

if(preg_match("/([A-Za-z0-9])+/", $to))

Answer 4

I think other answers regexps return true even if your string contains a single alphanumeric char in a string containing ALSO non-alphanumeric chars. (Try with "???alpha!!123" for exaple)

If you want to ensure your string contains ONLY alphanumeric chars, try this code:

if (preg_match("/^([[:alnum:]])*$/", $to))
{
    $errors[] = "Only use numbers and letters please";
}