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Asked: 2026-05-16T03:50:37+00:00

I am working on validating username, pass and email with php. I need to

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I am working on validating username, pass and email with php. I need to be sure I get it right so nobody can bypass the login page.

This is the values:

$email=$_POST['email'];
$username=$_POST['uname'];
$passwd=$_POST['pass'];
$passwd2=$_POST['passcopy'];

So far I have email validation:

if(!(preg_match("/^[\.A-z0-9_\-\+]+[@][A-z0-9_\-]+([.][A-z0-9_\-]+)+[A-z]{1,4}$/", $_POST['email'])))
    die(msg(0,"You haven't provided a valid email"));

password equal:

if ($passwd != $passwd2) {
die(msg(0,"Passwords are not equal"));
}

password length: 

if ((strlen($passwd) < 8) || (strlen($passwd) > 16)) {
die(msg(0,"Your password must be between 8 and 16 characters. Please type in a longer password"));
}

I know I need to validate the username. I was thinking only lowercase a-z0-9 to avoid people making similar usernames? Then password, what characters should I allow in a password?

PS. I still don’t understand preg_match and ereg. If somebody could explain this "/^[\.A-z0-9_\-\+]+[@][A-z0-9_\-]+ and make a preg_match for my username and password validation it would be very helpful.

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1 Answer

  1. Editorial Team

    the string ^[\.A-z0-9_\-\+]+[@][A-z0-9_\-]+ is a regular expression, that describes a pattern that you validate the email string against.

    Let me break the different parts down for you.

    ^ this indicates that the pattern should start matching at the beginning of the line.

    [\.A-z0-9_\-\+]+ this part is composed of two sub parts, first [\.A-z0-9_\-\+] that describes a class of characters, and then a + that indicates that you want one or more of the previous class.

    [@] matches exactly one @ sign.

    [A-z0-9_\-]+ another class of characters with a + after that means that you want one or more of the characters that are in the class.

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