Get a unique random integer.

unique_rand.php

<?php

/**
 * Get a unique random integer.
 *
 * @author Craig Anderson <craiga@craiga.id.au>
 * @link https://gist.github.com/craiga/6085988
 */
function unique_rand($min = 0, $max = null) {
	static $prev = array();
	if(is_null($max)) {
		$max = getrandmax();
	}
	do {
		$n = rand($min, $max);
	} while(in_array($n, $prev));
	$prev[] = $n;
	return $n;
}