Zufallsstring aus Zahlen und Buchstaben mit variabler Länge erzeugen

Dieses PHP-Script erzeugt einen Zufalls-String mit definierbarer Länge, bestehend aus zufälligen Zahlen und Buchstaben.

<?php
/*
    This Software returns random chars a-z/0-9 with given maxlength.

    Copyright (C) 2020  Guido Richter / tintenkobold.de

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License [http://www.gnu.org/licenses/] for more details.
*/

// output string length: $charNbr

function random_chars($charNbr)
{
	$chars = array('0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z');
	$randomchar = '';
	for($i=0;$i<$charNbr;++$i)
	{
		$randomchar .= $chars[rand(0,35)];
	}
	return $randomchar;
}

?>