gistfile1.php

<?php

function password_parts_message($password) {
    $upper = 0;
    $upperLetters = array();
    $lower = 0;
    $numbers = 0;
    $special = 0;
    
    $length = strlen($password);
    for ($i = 0; $i < $length; $i++) {
        $ascii = ord($password[$i]);
        if ($ascii >= 48 && $ascii <= 57) {
            $numbers++;
        } else if ($ascii >= 65 && $ascii <= 90) {
            $upper++;
            $upperLetters[] = $password[$i];
        } else if ($ascii >= 97 && $ascii <= 122) {
            $lower++;
        } else {
            $special++;
        }
    }
    
    if ((0 === $upper && $lower > 0) || (0 === $lower && $upper > 0)) {
        // All one case
        $case = (0 === $upper ? 'lower case' : 'upper case');
        $plus = array();
        if ($numbers) {
            $plus[] = 'numbers';
        }
        if ($special) {
            $plus[] = 'special characters';
        }
        
        $message = 'Please note that your password is all ' . $case;
        if (count($plus)) {
            $message .= ' letters plus ' . implode(' & ', $plus);
        }
        
        return $message;
    } else {
        // Mixed case
        if (1 === $upper) {
            return 'Please note that the "' . $upperLetters[0] . '" in your password is upper case';
        } else {
            $lastLetter = array_pop($upperLetters);
            return 'Please note that the "' . implode('", "', $upperLetters) . 
                '" and "' . $lastLetter . '" in your password are ' .
                (2 == $upper ? 'both' : 'all') . ' upper case';
        }
    }
}

// EXAMPLES
// -----------------------------------------------------------------------------

password_parts_message('LOL'); // Please note that your password is all upper case
password_parts_message('LOL012'); // Please note that your password is all upper case letters plus numbers
password_parts_message('LOL012!@#'); // Please note that your password is all upper case letters plus numbers & special characters
password_parts_message('LOL!@#'); // Please note that your password is all upper case letters plus special characters
password_parts_message('lol'); // Please note that your password is all lower case
password_parts_message('lol101'); // Please note that your password is all lower case letters plus numbers
password_parts_message('lol101!@#'); // Please note that your password is all lower case letters plus numbers & special characters
password_parts_message('lol!@#'); // Please note that your password is all lower case letters plus special characters
password_parts_message('Iol'); // Please note that the "I" in your password is upper case
password_parts_message('IOl'); // Please note that the "I" and "O" in your password are both upper case
password_parts_message('IOIlol'); // Please note that the "I", "O" and "I" in your password are all upper case