ขอสอบถามเรื่อง Array หน่อยครับ ให้ return "true", "false"

<?php
include ('paging.inc.php');
$request = trim(strtolower($_REQUEST['username']));
					
$sql = "select username FROM member ORDER BY 'member_id'";
$query = mysql_query($sql);
while($row = mysql_fetch_array($query, MYSQL_ASSOC)) { 
				$result[] = $row;
				}
                              //  $a = array('asdf', 'Peter', 'Peter2', 'George'); เช็คได้
				$a = array($result);
				print_r($a);

			    
				$valid = 'true';
				foreach($a as $user) {
				if( strtolower($user) == strtolower($request))
					{
						$valid = 'false';
					}

				}	
				echo $valid;

?>

<?php
include ('paging.inc.php');
			
$sql = "SELECT * FROM member WHERE username = '".trim($_REQUEST['username'])."' ";
$query = mysql_query($sql);
$users = mysql_fetch_array($query);
if($users)
				{
				$valid = 'false';
				}else{
				$valid = 'true';
				}
				echo $valid;
?>