PHP: Regex alphanumeric and some special characters only

Question

I want to use a regex to limit the characters allowed. That is:

a - z /* a to z */
A - Z /* A to Z */
0 - 9 /* 0 to 9 */
_ - /* underscore & dash */
~ ! @ # $% ^ & * () /* allowed special characters */

and this is my regex function:

function validChr($str) {
    return preg_match('/^[A-Za-z0-9_~\-!@#\$%\^&*\(\)]+$/',$str);
}

I've actually tried it and the result as I want, but I still was not sure. Is my regex is correct? Or are there other forms regex? Please help as I am still new about this regex. Thank you.

It's OK, but you should add an escape symbol for * as well, since it's a wildcard (in your code it means 'no or any amount of & sign in string'). — Rodion Baskakov
– Rodion Baskakov, Commented Nov 29, 2012 at 8:04
@RodionBaskakov If * it's between square brackets, I believe you don't have to escape it. — Pigueiras
– Pigueiras, Commented Nov 29, 2012 at 8:08
@RodionBaskakov: to be like this preg_match('/^[A-Za-z0-9_~\-!@#\$%\^&\*]+$/',$str); ? — Fredy
– Fredy, Commented Nov 29, 2012 at 8:08

Matija · Accepted Answer · 2012-11-29 08:14:00Z

9

It works as it should.

You should only add \ before * to escape it.

Check it out here: Regular expression test

answered Nov 29, 2012 at 8:14

Matija

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1 Comment

Anirudha Over a year ago

yes..but no need to escape * if it's within a character class

Raj Nandan Sharma · Accepted Answer · 2018-12-26 06:23:44Z

You can use this function I made sometime ago for passwords. You can use it for any string by modifying the if coniditions. Put each special characters with a \ before. It also has a check for string to be 8-20 characters long

    function isPasswordValid($password){
            $whiteListed = "\$\@\#\^\|\!\~\=\+\-\_\.";
            $status = false;
            $message = "Password is invalid";
            $containsLetter  = preg_match('/[a-zA-Z]/', $password);
            $containsDigit   = preg_match('/\d/', $password);
            $containsSpecial = preg_match('/['.$whiteListed.']/', $password);
            $containsAnyOther = preg_match('/[^A-Za-z-\d'.$whiteListed.']/', $password);
            if (strlen($password) < 8 ) $message = "Password should be at least 8 characters long";
            else if (strlen($password) > 20 ) $message = "Password should be at maximum 20 characters long";
            else if(!$containsLetter) $message = "Password should contain at least one letter.";
            else if(!$containsDigit) $message = "Password should contain at least one number.";
            else if(!$containsSpecial) $message = "Password should contain at least one of these ".stripslashes( $whiteListed )." ";
            else if($containsAnyOther) $message = "Password should contain only the mentioned characters";
            else {
                $status = true;
                $message = "Password is valid";
            }
            return array(
                "status" => $status,
                "message" => $message
            );
    }

Output

$password = "asdasdasd"
print_r(isPasswordValid($password));
// [
//   "status"=>false,
//   "message" => "Password should contain at least one number."
//]

$password = "asdasd1$asd"
print_r(isPasswordValid($password));
// [
//   "status"=>true,
//   "message" => "Password is valid."
//]

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