PHP random password generator - contains at least one lower case letter, one upper case letter, one number and one special character,

randomPassword.php

//generates a random password of length minimum 8 
//contains at least one lower case letter, one upper case letter,
// one number and one special character, 
//not including ambiguous characters like iIl|1 0oO 
function randomPassword($len = 8) {

    //enforce min length 8
    if($len < 8)
        $len = 8;

    //define character libraries - remove ambiguous characters like iIl|1 0oO
    $sets = array();
    $sets[] = 'ABCDEFGHJKLMNPQRSTUVWXYZ';
    $sets[] = 'abcdefghjkmnpqrstuvwxyz';
    $sets[] = '23456789';
    $sets[]  = '~!@#$%^&*(){}[],./?';

    $password = '';
    
    //append a character from each set - gets first 4 characters
    foreach ($sets as $set) {
        $password .= $set[array_rand(str_split($set))];
    }

    //use all characters to fill up to $len
    while(strlen($password) < $len) {
        //get a random set
        $randomSet = $sets[array_rand($sets)];
        
        //add a random char from the random set
        $password .= $randomSet[array_rand(str_split($randomSet))]; 
    }
    
    //shuffle the password string before returning!
    return str_shuffle($password);
}