php正则判断大小写

	if(isset($userget)){
			$userzz = "/^([a-zA-Z])[_a-zA-Z0-9]+$|^[1-9][_a-zA-Z0-9]+$/";
			$userzzz = "/^[A-Z]+$/";
			preg_match($userzz, $getuserss, $userarr);  
			preg_match($userzzz, $userarr[1], $usera);   
		if ($userget == "") {   
			echo iconv("GBK","utf-8","用户名不能为空");
		}else 
		if (strlen($getuserss) < 3) {
			echo iconv("GBK", "utf-8", "用户名不能少于3个字符");
		}else if ($getuserss == $rows['user']) {
				echo iconv("GBK", "utf-8", "用户已存在");
			}else if ($userarr == true) {   //判断起始大小写
			    if ($usera == true) {
			    		echo iconv("GBK", "utf-8", "起始位不能大写");
			    }
			}
			else {
				echo iconv("GBK","utf-8","用户名格式错误");
			}
		exit;	
		}