Sort emails by domain and mailbox

gistfile1.php

/**
 * Sort an array with emails by their domains and mailbox
 * ------------------------------------------------------
 * Input:
 *		array(
 *			'bbb@ccc.de',
 *			'bbb@bbb.de',
 *			'ccc@aaa.de',
 *			'aaa@aaa.de',
 *			'aaa@bbb.de'
 *		);
 *
 * Output:
 *		array(
 *			'aaa@aaa.de',
 *			'ccc@aaa.de',
 *			'aaa@bbb.de',
 *			'bbb@bbb.de',
 *			'bbb@ccc.de'
 *		);
 * ------------------------------------------------------
 * @param Array
 * @return Array
 */

function sort_emails(array &$emails){

	function sort_by_domain($a, $b){
	
		list($aMailbox, $aDomain) = explode('@', $a);
		list($bMailbox, $bDomain) = explode('@', $b);

		if( $aDomain == $bDomain ){
			
			return ($aMailbox < $bMailbox)? -1 : 1;

		}
	
		return ($aDomain < $bDomain)? -1 : 1;

	}

	usort($emails, 'sort_by_domain');

}