Question

I’m writing a password strength checker in PHP, and I’m using Regular Expressions to calculate various parameters for the strength calculation. I need to be able to check the number of repeating consecutive characters in a string. For example:

baaabaaablacksheep would return 5

sillystring would return 1

and so on...

Answer 1

You can use regex with \1+ to find the repeating characters, and then use strlen() to count them. Try something like:

$str = 'baaabaaablacksheep';    
$repeating = array();
preg_match_all('/(\w)(\1+)/', $str, $repeating);

if (count($repeating[0]) > 0) {
    // there are repeating characters
    foreach ($repeating[0] as $repeat) {
        echo $repeat . ' = ' . strlen($repeat) . "\n";
    }
}

Output:

aaa = 3
aaa = 3
ee = 2