1.我们经常接收到网址get字符串，需要将字符串转成成数组使用

$str="tn=a&ie=utf-8&bs=httpbuildurl&f=3"
$data = [];
parse_str($str,$data);
var_dump($data);

2.我们经常需要将数组转化成字符串

$data = [
     'tn'=>a,
     'utf-8'=>httpbuildurl,
     'f'=>3
];

$url = http_build_query($data);

//输出tn=a&ie=utf-8&bs=httpbuildurl&f=3