PHP 中如何創建和修改數組？

PHP中使用array來創建一個數組:array( key=>value , key=>value …… )
用方括號的語法來修改數組:$arr[] = value

例如：
$arr = array(3,5,7,9);
$res = array(“a” => “視頻”, “b”=>”教2程”, “c” => “六”);

$arr['a'] = “老溫”;
$arr['c'] = “試題”;