Generate a random string.

randomstring.php

<?php

/**
 * Generate a random string.
 * 
 * Based on {@link https://gist.github.com/craiga/4075392 a JavaScript function}.
 * 
 * @param $alphabet (optional)   The alphabet used to generate a random string.
 * @param $minLength (optional)  The minimum length of the string. 10 by default.
 * @param $maxLength (optional)  The maximum length of the string. 20 by default.
 *
 * @author Craig Anderson <craiga@craiga.id.au>
 * @link https://gist.github.com/craiga/fc0aec6cc988d2029928
 */
function randomString($alphabet = null, $minLength = 10, $maxLength = 20) {
	if(is_null($alphabet)) {
		$alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
	}
	$s = "";
	$alphabetLength = strlen($alphabet);
	$length = rand($minLength, $maxLength);
	for($i = 0; $i < $length; $i++) {
		$s .= substr($alphabet, rand(0, $alphabetLength - 1), 1);
	}
	return $s;
}