Detect common Password/PIN

I Made a PIN authentication on my website, and I don’t want my user using common PINs like 12345, 11111, 121212, etc.

I tried this

    if($PIN=="111111" || $PIN="222222"){
   
    echo "This PIN is common";
}

But I think that Will be too long for a simple function? How to simplify it?

Answer

Your problem is actually quite simple, you want, for example, to avoid pins that have multiples iterations of a same character in a row OR/AND avoid pins that have a same character repeated more than X times in a string.

Using Regex we can easily achieve something like this: For example, the following will return 1 if 3 characters or more are in a row.

<?php
$pin = '111025'; 
if ( preg_match( '/(.)1{2}/', $pin ) ) {
  return true;
} else {
  return false;
}; ?>

---

Learn more

RegEx.
A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.

Function	Description
preg_match()	Returns 1 if the pattern was found in the string and 0 if not
( )	You can use parentheses ( ) to apply quantifiers to entire patterns. They also can be used to select parts of the pattern to be used as a match
.	Find just one instance of any character
n{x}	Matches any string that contains a sequence of X n’s

PHP RegEx @ https://www.w3schools.com/php/php_regex.asp