Source: http://php.net/manual/en/function.random-bytes.php

Usage: Generating CSRF token, verification token, ..etc

function RandomToken($length = 32){
    if(!isset($length) || intval($length) <= 8 ){
      $length = 32;
    }
    if (function_exists('random_bytes')) {
        return bin2hex(random_bytes($length));
    }
    if (function_exists('mcrypt_create_iv')) {
        return bin2hex(mcrypt_create_iv($length, MCRYPT_DEV_URANDOM));
    } 
    if (function_exists('openssl_random_pseudo_bytes')) {
        return bin2hex(openssl_random_pseudo_bytes($length));
    }
}

function Salt(){
    return substr(strtr(base64_encode(hex2bin(RandomToken(32))), '+', '.'), 0, 44);
}

echo (RandomToken());
echo "\n";
echo Salt();
echo "\n";

/*
This function is same as above but its only used for debugging
*/
function RandomTokenDebug($length = 32){
    if(!isset($length) || intval($length) <= 8 ){
      $length = 32;
    }
    $randoms = array();
    if (function_exists('random_bytes')) {
        $randoms['random_bytes'] = bin2hex(random_bytes($length));
    }
    if (function_exists('mcrypt_create_iv')) {
        $randoms['mcrypt_create_iv'] = bin2hex(mcrypt_create_iv($length, MCRYPT_DEV_URANDOM));
    }
    if (function_exists('openssl_random_pseudo_bytes')) {
        $randoms['openssl_random_pseudo_bytes'] = bin2hex(openssl_random_pseudo_bytes($length));
    }

    return $randoms;
}
echo "\n";
print_r (RandomTokenDebug());