Steam api用户数据：仅适用于一个蒸汽ID，否则DOESNT WORK

Question

I'm really new to php and doesnt understand much with apis.. I wrote this code:

<?php
$steamkey = "xxxxxxxx"; // censored I use the right steamkey
$id_user = "76561198059606697"; // only this steam id works

$apifr = "http://api.steampowered.com/ISteamUserStats/GetUserStatsForGame/v0002/?appid=730&key=".$steamkey."&steamid=".$id_user;

$data = file_get_contents($apifr); // put the contents of the file into a variable

$test = json_decode($data);

echo print_r($test->playerstats->stats[0]->value, true);
?>

the result is the total_kills of the player steam id:

49999

The result "49999" are the right total_kills of the player in csgo, which actually works just fine, but if I try different steamids it doesnt work anymore...

Could someone please help me and explain why or give another solution to use the steam api for csgo player stats?

Thank you all

I tried more then 10 different right steam ids, however they doesnt work... Some people have names instead of for example "1231943812" as a steam id, it doesnt work too, I dont know how to use the names too